In a final report heavily stitched with reservations and uncertainties, the House Assassinations Committee suggested yesterday that President Kennedy may have been killed in a conspiracy involving a patchwork assortment of gangland figures and anti-Castro activists.

The committee acknowledged, however, that it was difficult to see how they could have enlisted Lee Harvey Oswald for the murder. The House panel said it had no doubt that Oswald was the one who killed the president in Dallas' Dealey Plaza on Nov. 22, 1963.

The committee, which also investigated the murder of the Rev. Martin Luther King Jr. in Memphis on April 4, 1968, concluded that there was "substantial evidence to establish the existence of a St. Louis-based conspiracy to finance the assassination" of the civil rights leader.

The report contended that King's killer, James Earl Ray, may have beem motivated by rumors of the $50,000 bounty on King's life that some businessmen allegedly were offering.

With three members dissenting to the finding of a probable plot in the JFK case, the committee, however, held that "it was possible, based on an analysis of motive, means and opportunity, that an individual organized crime leader, or a small combination of leaders might have participated in a conspiracy to assassinate President Kennedy."

The 686-page final report, made public yesterday more than six months after the committee formally ceased operations, added:

"The committee's extensive investigation led it to conclude that the most likely family bosses of organized crime to have participated in such a unilateral assassination plan were Carlos Marcello and Santo Trafficante."

The committee also suggested that the former Teamsters union chief, James R. Hoffa, may have played a role in the killing because he, too, "had the motive, means and opportunity for planning an assassination attempt" on the president's life and because he had once actually spoken of having the president's brother, Robert F. Kennedy, killed.

But having said all that, the committee gingerly backed off, pronouncing that it was "inlikely" after all that New Orleans Cosa Nostra leader Marcello or Tampa underworld chieftain Trafficante was involved. Similarly, after raising the question of Hoffa's possible complicity at a time when the Kennedy administration was trying to put him in prison, the report stated:

"It may be strongly doubted, therefore, that Hoffa would have risked anything so dangerous as a plot against the president at a time that he knew was under active investigation by the Justice Department."

With only seven of its members voting, the committee reached its central conclusions last Dec. 29, including the especially controversial finding that Kennedy was "probably assassinated as the result of a conspiracy."

A committee majorilty was convinced by a detailed acoustical study of the noises in Dealey Plaza that there was "a high probability that two gunmen fired" at Kennedy within a split-second sequence, Oswald shooting from the Texas School Book Depository behind the president and an unknown sniper firing from the so-called "grassy knoll" to the right of the presidential motorcade.

Since those findings were made, a skeleton committee staff, headed by chief counsel G. Robert Blakey, has been putting together the final report, and companion volumes, to back them up. Blakey, for one, says he believes even more strongly than the report suggests that organized crime figures were somehow responsible for the president's murder.

"This committee report does not say the mob did it," Blakey has stated. "I said it. I think the mob did it."

Shades of Garrison

The report is redolent, in many details, of former New Orleans district attorney Jim Garrison's baroque investigation of the JFK assassination in 1967-68. The committee, however, insisted that it had been much more careful with its facts.

"Aware that Garrison had been fairly criticized for questionable tactics," the report stated, "the committee proceeded cautiously, making sure to determine on its own credibility of the information coming from his probe."

Strikingly, some of the most startling findinds, along with accompanying hints and touches, were based on secret interviews and depositions, which have yet to be made public, rather than evidence adduced at the committee's open hearings last year.

Witnesses from Clinton, La., who said they saw Oswald in the company of late airline pilot David W. Ferrie, a prime suspect of Garrison's were, for instance, all questioned in executive sessions. So was Marcello, who, the report discloses, testified under a grant of immunity more than a year ago, on Jan. 11, 1978.

Some of the highlights of the report:

Oswald in New Orleans

The ex-Marine and erstwhile defector to Russia stayed in New Orleans in the summer of 1963, posing what the committee called "an especially puzzling period" in his life.

"His actions," the committee pointed out, "were blatantly pro-Castro, as he carried a one-man Fair Play for Cuba Committee crusade into the streets of a city whose Cuban population was predominantly anti-Castro. Yet Oswald's known and alleged associations even at this time included Cubans who were of an anti-Castro persuasion and their anticommunist American supporters."

Not long after a street scuffle with anti-Castro activists on Aug. 9, 1963, over his pro-Castro pamphleteering, Oswald "largely passed out of sight, from Aug. 21 until Sept. 17, the day he applied for a tourist card to Mexico."

Sometime during that interval, the report contends, Oswald apparently turned up in Clinton, La., "in the company of David Ferrie, if not Clay Shaw," who was another target, before he died, of Garrison's investigations.

The committee said it had six witnesses from Clinton, among them a state representative, a deputy sheriff and registrar of voters, each of whom was "interviewed, or deposed, or appeared before the committee in executive session."

According to a synthesis of their testimony, Oswald first showed up in the late summer in nearby Jackson, La., looking for a job at the East Louisiana State Hospital.

But there, the report said, he was apparently told he had to be a registered voter, and so went on to Clinton, the country seat of East Feliciana Parish (Country) 130 miles from New Orleans.

The committee said it found no record that Oswald managed to register as a voter, but it said the physical descriptions and other observations provided by the witnesses "tended to substantiate their belief that he was, in fact, the man they saw.

For example," the report stated, "he referred to himself as 'Oswald,' and he produced his Marine Corps discharge papers as identification. Some of the witnesses said that Oswald was accompanied by two older men whom they identified as Ferrie and Shaw."

The House investigators added cautiously, without quite committing themselves: If the witnesses were not only truthful but accurate as well in their accounts, they established an association of an undetermined nature between Ferrie, Shaw and Oswald less than three months before the assassination."

Rumors swirling about Jim Garrison's investigations a decade ago often emphasized suspected homosexual of anti-Castro proclivities at the bottom of it all, but the House committee, while acknowledging that Ferrie was "a staunch anti-Castro partisan,"saw more significance in his ties to Marcello.

Ferrie's Connections

A former airline pilot, private detective, amateur hypnotist and patron of young men, Ferrie had once commanded a Civil Air Patrol unit in New Orleans in the 1950s, when Oswald joined the CAP, although Ferrie always denied having known Oswald. In 1963, having been fired by Eastern Airlines, Ferrie was embroiled in litigation over his dismissal, and had as his lawyer a New Orleans attorney named G. Wray Gill.

Relying heavily on a still unpublished committee staff study, the report said:

"Ferrier later stated that in March 1962 he and Gill made an agreement whereby Gill would represent Ferrie in his dismissal dispute in return for Ferrie's work as an investigator on other cases. One of these cases involved deportation proceedings against Carlos Marcello, the head of the organized crime network in Lousiana and a client of Gill."

The report said Ferrie also stated he had entered into a similar agreement with Guy Banister, a former FBI agent who operated a private detective agency in a New Orleans building at 544 Camp St. Oswald, as well as anti-Castro groups, also claimed 544 Camp St. as a mailing address.

"During the summer of 1963, Ferrie frequented 544 Camp St. regularly as a result of his working relationship with Banister," the report said. "The committee also found that there was at least a possibility that Oswald and Guy Banister was acquainted."

Carlos Marcello

Ferrie may have been connected with Marcello even before Ferrie began working on the reputed crime chief's legal proceedings, according to the committee.

In April 1961, Marcello had been abruptly picked up in New Orleans and shipped out of the country by federal agents via what one knowledgeable source has told The Washington Post was "a black [illegal] flight" to Guatemala. In any case, Marcello made his way back to the United States secretly some time later.

"An unconfirmed U.S. Border Patrol report indicated that in February 1962, Ferrie piloted an airplane that returned Marcello to the United States," the committee said. Marcello denied this to the committee and insisted that "he flew commercial airlines."

Of Marcello, the report also said that in his executive session testimony before the House committee he "exhibited an intense dislike for Robert Kennedy" because of the deporttation effort. Marcello felt "he had been illegaly 'kidnaped' by government agents. . ."

The committee said it also found "associations" between Jack Ruby, who killed Oswald on Nov. 24, 1963, and "several individuals affiliated with the underworld activities of Carlos Marcello," such as Joseph Civello, a "Marcello associate who allegedly headed organized crime activities in Dallas."

But having said all that and more, including the admittedly questionable account of an underworld informer about Marcello's once having threatened Kennedy's assassination, the report observed that "Marcello's uniquely successful career in organized crime has been based to a large extent on prudence. . Considering that record of prudence, and in the absence of direct evidence of involvement, it may be said that it is unlikely that Marcello was in fact involved in the assassination of the president."

For his part, Marcello denied to the committee any such involvement.He also denied ever making any kind of threat against the president.

Santo Trafficante

One of "10 top syndicate leaders targeted for investigation in the Kennedy administration," Trafficante was working at the same time with the CIA in plotting Cuban Premier Fidel Castro's assassination. The House committee said it established several possible connections between Trafficante and Jack Ruby, going back as far as 1959, during a Ruby visit to Havana.

Sometime in September of 1962, Trafficante reportedly told a promnent Cuban exile, Jose Aleman, that Kennedy was "going to be hit," and gave Aleman "the distinct impression that Hoffa was to be principally involved in planning the president's murder.

In 1963, in a conversation "overheard in a Miami restaurant, Trafficante had bitterly attacked the Kennedy administration's efforts against organized crime, making obscene comments about 'Kennedy's right-hand man,' who had recently coordinated various raids on Trafficante gambling establishments."

Nonetheless, the report hedged, "As with Marcello, the committee noted that Trafficante's cautious character is inconsistent with his taking the risk of being involved in an assassination plot against the president."

James Earl Ray

The committee, whose investigations cost some $5.4 million, reiterated its finding that James Earl Ray fired the single rifle shot that killed King, but the report added that "on the basis of circumstantial evidence. . . there is a likelihood" that the murder was the result of a conspiracy.

The speculation here centered on the notion that Ray, while serving time in a Missouri state prison, heard of a $50,000 bounty being offered by a St. Louis group for King's life. The committee said it had no proof tying Ray to the purported offer, but said it still felt that "his act did not stem from racism alone. . . His predominant motive lay in an expectation of monetary gain."

Ray, the report suggested, "may simply have been aware of the offer of payment after the assassinantion. Or he may have acted, not only with an awareness of an offer, but also after reaching a specific agreement." The committee acknowledged, however, that it had no evidence of such an agreement.

Similarly, the report said the committee's evidence "raised the possibility of the involvement" of either or both of Ray's brothers, John and Jerry, but it steered away from any definite conclusions.

In any event, the committee said it was unable "to identify significant associates of the assassin other than his brothers. . . The possibility of their involvement owas necessarily increased by the absence of alternatives." CAPTION: Picture 1, LEE HARVEY OSWALD . . . still considered JFK killer;Picture 2, CARLOS MARCELLO . . . denied making any threat;Picture 3, JAMES EARL RAY . . . panel cites "bounty" rumor