Airlie Foundation director Murdock Head paid $49,000 in bribes -- mainly to two congressmen he referred to as "the mustache" and "the priest" for help in securing federal funds for his foundation, a key prosecution witness testified yesterday.

Those congressmen were mustachioed Rep. Daniel J. Flood (D-Pa.), referred to as "Mandrake" in addition to "the Mustache," and former Rep. Otto E. Passman (D-La.), according to the witness, Stephen B. Elko, Flood's former administrative assistant.

Elko told a federal jury that Head gave him the payoffs during a series of furtive meetings at the foundation's Warrenton, Va., headquarters between 1971 and 1974. He said he passed on $28,000 to Flood and $12,000 to Passman. Elko acknowledged he kept $9,000 himself.

"I earned a few bucks too," the soft-spoken conservatively dressed Elko quipped at one point as he explained why he kept some of the alleged bribe money.

Elko, who is currently on parole from a two-year prison sentence in a separate case, testified on the second day of Head's conspiracy, bribery and tax-evasion trial in U.S. District Court in Alexandria.

Dr. Head, 55, who is also a George Washington University professor and department chairman, directs the tax-exempt Airlie Foundation, which sprawls over more than 1,700 acres in the foothills of the Blue Ridge Mountains about 50 miles west of Washington. The foundation has carried out numerous government projects and attracted high-ranking officials to its conferences and projects.

Elko's testimony yesterday was similar to that he gave in Flood's first bribery trial which ended in a hung jury last February. The congressman's retrial has been delayed because of his poor health.

Passman was acquitted, in an unrelated criminal proceeding, of charges that he received bribes from South Korean businessman Tongsun Park in exchange for his congressional influence. He has not been charged with receiving the bribes Elko allegedly passed on to him from Head.

Elko told the jury in Alexandria yesterday that Head often referred to prominent men by code names, used facial tissue to avoid leaving fingerprints on the alleged bribe money and gave Elko his "super-unlisted" telephone number.

Elko told the jury about a December 1973 incident during which Head allegedly called him in to a motion picture screening room at Airlie headquarters because Head "was very concerned about electronic surveillance." During the meeting, Elko testified, Head wrote on an easel, "'The long knives are out.' He [Head] was was going fishing for about a year. 'I think you Elko better duck. The cannon balls are flying.'"

Then, Elko said, they bargained over the amount of the next payoff, with Elko asking for $15,000 and Head offering $5,000. They compromised on $8,000, Elko said.

Elko told the jury that the alleged payoffs were mainly in exchange for help from Flood and Passman in arranging grants for Airlie Foundation from the Department of Health, Education and Welfare and the Agency for International Development. One AID grant cited by Elko provided for up to $1 million annually to Airlie for five years.

During one 1972 payoff session, Elko testified, Head urged him to turn over $5,000 to Flood and tell Flood to give the money to Passman. But Elko said he replied, "I would give it to Mr. Passman myself because if Flood ever got his hands on it, nobody would ever see it again."

Brian P. Gettings, one of Head's lawyers, quickly sought to tear apart Elko's testimony." It's our contention that this man's testimony is a fabrication," Gettings told presiding Judge Oren R. Lewis after the jury had been excused at the end of yesterday's court session.

Under cross-examination by Gettings, Elko remained calm and unflappable. He acknowledged that he had been convicted of perjury, obstruction of justice and other charges in a bribery scheme involving a California vocational school and that he was testifying under a grant of immunity from further criminal prosecution.

He admitted that he had given varying accounts of the same alleged incidents in interviews with FBI agents, statements to congressional committees and testimony during the Flood trial. These discrepancies included differing versions of when the incidents allegedly occurred, varying amounts of the alleged payoffs and inconsistent accounts of precisely what was said by Head, Flood and others.

Elko responded to Gettings' wideranging attack by saying that his accounts of the alleged incidents had been "modified" only in relatively minor details and had "substantially not changed" in any major way.

Earlier in the day, the prosecution presented further testimony to back up its contention that Head directed a scheme of falsifying financial records to create a slush fund to pay bribes. Charles E. Francis, former president of a film making firm linked with Airlie, testified that the alleged cash fund amounted to about $90,000 in 1978.