A LOT OF people wish it would go away permanently, but the murder of John F. Kennedy now begs, more than ever, for serious detective work in search of conspiracy.

Beyond the mechanics of what happened in Dealey Plaza, we are now confronted with larger questions and the elusive outline, at least, of a plausible conspiracy. This is certainly not the time to heave a collective sigh and let it drop, but rather to pose the next question: What kind of conspiracy? Was it big or small, left or right, foreign or domestic?

It is still not widely understood that the House Select Committee on Assassinations developed two conspiracy arguments, not one, and that its original finding was not based on the sensational acoustics evidence that struck home late in December when the committee's time was all but over. Before the acoustics experts testified that they were "more than 95 percent certain" of having detected proof of a second gunman, other evidence had persuaded most committee members that a conspiracy was "likely." The acoustics findings jumped "likely" to "probable," but the basic decision had already been made by a majority of the committee and its senior staff.

That decision was based on circumstantial evidence indicating that Lee Harvey Oswald, lone gunman as he may or may not have been, and Oswald's killer, Jack Ruby, were quite possibly under the control or influence of mob figures now known to have been threatening the lives of both John and Robert Kennedy.

The chief of these was Carlos Marcello of New Orleans, regared by experts on the mob as one of the most powerful Mafia bosses in the country, just below Meyer Lansky and the New York Gambino family. Now aging, Marcello still bosses a crime system whose take in Louisiana alone has been estimated by the New Orleans Crime Commission at over $1 billion a year. His influence extends through the Southwest, including Dallas.

The committee staff's initial conspiracy theory had the peculiar property -- and perhaps the virtue -- of justifying both sides in this long and often acrimonious debate. To the Warren Commission and its children, it gave support for the view that Oswald was the only gunman of Dealey Plaza. To the critics, it gave support for the theory that Oswald was linked to a larger conspiracy that recruited or duped him.

If the committee is right about the acoustics evidence, then clearly any lone-gunman theories are forever obviated.But that only makes more important the evidence suggesting Oswald and Ruby ties to the mob. The committee's detailed final report, due at the end of March (an outline was released Dec. 30), is expected to present a highly textured picture of these relationships. A Substitute Father

THE OSWALD link to Marcellobears on his relationship to threemen during 1963 -- Charles (Dutz) Murret,David Ferrie and W. Guy Banister.

Murret is mentioned in the Warren Report but identified only as Oswald's uncle. According to committee sources, Dutz was Oswald's substitute father during his childhood.Oswaldapparently was attached to him. When Oswald moved from Dallas to New Orleans, his birthplace, in April 1963, it was uncle Murret who initially put him up while he looked for work and a place to bring his family.

What you will not find in the Warren Report, however, is information developed by the House committee that Dutz Murret was not your run-of-the-mill uncle. According to recently retired New Orleans Crime Commissioner Aaron Kohn, Murret, who died 1964, was an important bookie tied into New Orleans organized crime. As such, according to Kohn, he "certainly knew who Marcello was."

A House committee source goes further, calling Murret "a top deputy of a top man in Carlos Marcello's gambling apparatus." Adds this source: "Oswald was aware of his uncle's [organized crime] ties and discussed them with him in 1963."

More intriguing is Oswald's relationship with David Ferrie, which was rediscovered and confirmed by the House committee (Jim Garrison's investigation was onto the Ferrie link in 1967 when Ferrie died). We still have much to learn about it, but the tie is important because Ferrie is known to have worn two quite different hats.

Under one hat, he worked inside the Marcello operation. He was Marcello's personal pilot, the man who flew the crime lord back into the United States after Marcello's summary deportation to Guatemala in 1961 by Attorney General Robert Kennedy. Within the organization, he also was an "investigator" for Marcello's top lawyer and adviser. Ferrie was, in fact, at Marcello's side in court at the moment of the assassination.

Under his other hat, Ferrie was a contract operative for the CIA who had trained pilots for the Bay of Pigs invasion.

When Oswald and Ferrie first met is still cloudy. The committee's final report will note that Oswald was a teenage cadet in the same Civil Air Patrol unit in which Ferrie was once a captain and instructor. Also unclear is when and how often the two met in New Orleans in 1963. The committee has been impressed by the credibility of three witnesses who said they saw Oswald on several occasions in Ferrie's company in Clinton, La.

Oswald and Ferrie also both occupied offices at the small building then standing at 544 Camp St., the address stamped on the pro-Castro leaflets Oswald passed out in August 1963 in downtown New Orleans. This building was then the headquarters of anti-Castro activity throughout the region.

The Camp Street operation was directed by an ex-FBI officer, W. Guy Banister, whose private detective agency was a cover for his role as gobetween for the CIA and the Cuban exiles involved in anti-Castro operations.

Marcello's man Ferrie also worked for Banister as a private investigator at that time. We know that Banister, aided by Ferrie, acted in the areas of gun-running and the training and staging of Cuban commandos. Banister's Camp Street office was surrounded by Cuban-exile organizations, including at one point the Cuban Revolutionary Council, a CIA front group set up by, among others, Antonio de Varona, the Cuban exile leader. It was Varona who received from mobster John Rosselli the poison pills which had come from the CIA and which were intended for the Castro brothers and Che Guevara.

Yet it was to this building, a hotbed of anti-Castro activity, that young Oswald, self-made Marxist, came to find an office for his pro-Castro one-man band, the New Orleans chapter of the Fair Play for Cuba Committee. "There has to be a connection between Oswald and those who operated in the building," says one House committee source.

Adding substance to this view, committee sources also confirm that they have found reliable eyewitness evidence that Oswald and Banister may have been together during the summer of 1963. At least one of these witnesses, retired CIA operative William Gaudet, first said publicy in a 1977 Canadian television documentary that he saw Oswald and Banister together at a New Orleans garage close to the Camp Street headquarters. Gaudet had not spoken of this earlier. According to a committee source, "he kept his mouth shut because that's what agency procedure was. Plus he's paranoid and thought he was going to be killed. And probably more importantly, nobody ever asked him."

The "nobody" included the Warren Commission, which concluded that "extensive investigation was not able to connect Oswald with that address," 544 Camp St. This apparently was because the FBI withheld information on the point. The House committee knows, as the Warren Commission did not, that the FBI had a pre-assassination file on Oswald linking him to that well-known address. The committee also knows, as the Warren Commission did not, that the 531 Lafayette St. address provided by the FBI as Banister's office was simply a side entrance to the Camp Street building. No Sudden Impulse

THE COMMITTEE also found evidence that Jack Ruby was acting under no sudden impulse when he murdered Oswald. The Warren Commission thought Ruby's act unpremeditated and accepted his story to the effect that sympathy for the president's widow was his only motive.

But the House investigation found indications that Ruby was stalking Oswald in the Dallas jail for at least a full day before he killed him, and that far from coming into the jailhouse basement via the driveway ramp, as the Warren Report had it, Ruby appears to have gone through an altogether different entrance and may well have had inside help in doing so.

The implication is that Ruby was out to keep Oswald from standing trial. Could Oswald, as he claimed, have implicated accomplices? Possibly acquitted himself in a trial? Identified those who might have framed him?

This raises the further question of what or whom Ruby was protecting. The Warren Commission concluded that "the evidence does not establish a significant link between Ruby and organized crime," even though in a secret meeting on Jan. 24, 1964, Warren Commission chief counsel J. Lee Rankin informed the commissioners that Ruby "has apparently all kinds of connections with the underworld." Indeed, House committee chief counsel G. Robert Blakey calls Ruby's presence in the story "the greatest single justification" for raising the question of mob involvement in the assassination.

Warren Commission members knew that Ruby's mob ties went back to the 1940s and that he went to Cuba in 1959. The House committee will report that he made at least three mob-related trips to Cuba that year. He met in prison with Florida crime boss Santos Trafficante, who had been jailed by Castro. He also met with his closest friend and Trafficante's manager at the Tropicana casino, Lewis McWillie. His aim included helping smuggle Trafficante's cash out of the closed casino and back to the United States.

The Warren Commission also knew that in the two months before the assassination, Ruby was in telephone contact with key figures of the New Orleans, Chicago and Florida crime families. Initiated by Ruby, who somehow had access to their unlisted phone numbers, these calls went to mobsters Barney Baker, a feared enforcer for Teamster boss Jimmy Hoffa; Lenny Patrick, a hired killer working for Chicago boss Sam Giancana; Nofio Pecora, one of Marcello's most trusted aides; and Trafficante's man, McWillie.

Ruby also talked to Murray (dusty) Miller, a national Teamsters official close to Hoffa, and Irwin S. Weiner, chief Teamsters bondsman and a top Hoffa adviser. On Nov. 20, 1963, two days before JFK was shot, Ruby was visited at his nightclub by another notorious mobster, Paul Roland Jones. And on the next night, Ruby had drinks with a friend who had been in recent phone contact with Marcello's aide and Oswald's friend, David Ferrie.

So what? So Ruby was a hood. So Oswald hung around with a few colorful types in New Orleans. What's the angle? What could it add up to? The answer may lie in the tangled, turbulent history set in motion by the Cuban revolution of 1959. The Mob and the CIA

MOST OF US are aware that before the Cuban revolution the Mafia held a strong position in Havana, controlling vice and gambling rackets through an arrangement between Cuban strongman Fulgencio Batista and U.S. crime boss Meyer Lansky. When Castro overthrew Batista in early 1959, he expropriated and closed Havana's casinos and jailed or banished their owners or operators. That infuriated the mobsters -- especially Marcello's ally, Santos Trafficante, whom Castro imprisoned.

Trafficante and Marcello were the pillars of a southern wing of the crime syndicate, and Cuba was vital to them. No sooner had Castro driven them out than they started plotting how to get back in, wondering how to get rid of Castro.

Others were pondering the same problem, notably Vice President Richard Nixon, who was then the ranking political member of the National Security Council's so-called 5412, or Special Group, which would essentially decide (during Eisenhower's illness) what U.S. policy would be toward Castro. Nixon interviewed Castro privately when Castro came to New York to the United Nations in 1959 and concluded that he was a threat to U.S. security and would have to go.Plans for the invasion of Cuba were drawn up and set in motion before 1959 was out.

By August 1960, at latest, about the time JFK was being nominated as the Democratic presidential candidate, Allen Dulles' CIA had initiated its now infamous arrangement to have Castro killed by the Mafia. Thus, two powerful covert organizations, the CIA and the Mafia, were secretly joined for a joint strike against Castro.

Kennedy's election meant the invasion would occur under a president who hadn't been in on it from the start and who didn't share Nixon's anti-Communist zeal. Kennedy had tried to look even tougher than Nixon on Cuba during the campaign, but once in office he limited U.S. participation in the invasion. He rejected the CIA proposal to kill Castro (according to the Church Committee) and refused to unleash CIA B-26s waiting in Guatemala to support the strike.

Everyone came out of the Bay of Pigs fiasco infuriated. Kennedy fired future Warren Commission member Allen Dulles from the CIA and promised to "splinter" the CIA "into a thousand pieces" for having deceived him on Cuban feelings toward Castro.

The invasion team and its partisans said Kennedy had betrayed them at the beach. He betrayed them again, they said, in the October 1962 missile crisis when he secretly promised Soviet Premier Nikita Khrushchev that he would stop the exiles' commando raids against Cuban targets, raids staged from bases in Florida and Louisiana -- home territories, respectively, of Trafficante and Marcello. The Anti-Crime Drive

IT WAS NOT Cuba alone, of course, that drove the mob to flash-point anger with the Kennedys. There was motive enough in the campaign to extirpate the mob from U.S. life.

RFK had had Marcello physically seized off a New Orleans street and deported to Guatemala in April 1961 (two weeks before the Bay of Pigs), without giving him a chance to see a lawyer or pack a bag. When Marcello reentered the country two months later in a private plane piloted by Oswald's soon-to-be-made acquaintance, David Ferrie, he was already in a state of permanent rage over the Kennedy brothers. Specifically angry with Robert Kennedy, the mobster, according to a House committee informant, also fulminated against the president in September 1962, citing a Sicilian adage that to kill a rooster "you don't cut off the tail, you cut off the head," and adding that JFK should be killed "by some nut." About the same time, Marcello ally Trafficante told Cuban exile leader Jose Aleman not to worry about JFK: "He's going to be hit."

Teamsters leader Hoffa, close to Marcello, was possibly even angrier at the Kennedys. Hoffa, whohad become RFK's special target, was finally about to be imprisoned. According to a House committee source, "The Hoffa threat [against RFK] is absolutely confirmed. We believe it and [our final report] will say so."

The committee has learned that in August 1962, in Hoffa's Washington office, he discussed two plans to kill RFK. The first was to firebomb RFK's Virginia estate with plastic explosives. The second was to shoot him with a high-powered rifle as he rode in his convertible in a southern city.

The committee will not pretend that it has found a smoking gun to support its Mafia theory. Nor will it say that the 1962 expressions of murderous hatred for the Kennedys by Marcello, Trafficante and Hoffa prove that they were embarked upon a JFK assassination plot as of that moment. Indeed, the committee's investigators find it unlikely that these threats would have been voiced before such low-level figures as Aleman or the Marcello informant if a plot actually had existed at the time.

The committee also will not pretend that it can clearly outline how a Marcello-Trafficante-Hoffa conspiracy would have selected and recruited Oswald, whether as assassin or patsy.

It will not explain (and chief counsel Blakey is known to be troubled about this) how some of the world's most hardened mobsters might let the weight of a supremely hazardous plot fall on an unknown quantity of the likes of Oswald. "What doesn't seem to add up," said JFK Subcommittee Chairman Richardson Preyer (D-N.C.) in early January, "is how other conspirators might have picked somebody as unstable as Oswald to carry out their plot."

What is important, though, is that the committee has established that Marcello, Trafficante and Hoffa all had motive, means and opportunity to assassinate the president, that the three were sufficiently close for individual motivates to have combined to produce an assassination conspiracy, and that they had access to Oswald and Ruby in the half year preceding the assassination.

The final committee report will tell what concrete opportunities exist for further investigation of the New Orleans angle. Chief Counsel Blakey has promised "to lay out in full detail the situation in New Orleans" in the final report: "What Oswald was up to and with whom he associated." A Question of Trust

WHAT ABOUT the larger meaning of it all?

Committee chairman Louis Stokes (D-Ohio), who helped rescue the panel from the shouting matches that nearly destroyed it in its first year, says, "All of us know that organized crime permeates the society. Society is helpless.... It is not powerless, but government utilizes that power only where they want to, and organized crime is not where they really want to use it."

Chief counsel Blakey has other thoughts. He is no firebrand. He is an Ivy League academic who does not express opinions impetuously. But, stepping out of his committee role for the first time publicly, this is what he told a meeting of lawyers on Jan. 25 in New York City:

"I can tell you that not one institation of my society served me well in 1963... The FBI did not adequately investigate the conspiracy... The CIA, what did they do for us?... The Warren Commission itself represented in many ways the best in our society... They studied the case as best they could, arrived at their judgments in good faith, and were fundamentally wrong on the conspiracy question.

"And they made what in my judgment was a serious mistake. They stated their judgment... as [though] they mistrusted the American people. They should have said, 'We've done the best we could, we know who shot the president, we're not sure whether others were involved,' and then trusted to the maturity of the American people to accept it as such.

"They didn't. And this let into our society a kind of poison that has run through the body politic since. We call it Watergate today -- a lack of credibility in governmental institutions. There are a lot of young people who have thought this case through who will never trust the government again...

"If there is any message to take out of this case, it can be summed up in two words -- never again ! The next time this happens -- and it will happen: one in four of our presidents has been shot at -- I hope indeed that people will have the courage and the integrity to stand up and say, 'I will pursue this as far as I can, and if I can't go all the way, because I'm human, I will tell people of that."