Four former government leaders, including Kennedy-Johnson administration defense secretary Robert S. McNamara and Carter administration secretary of state Cyrus R. Vance, yesterday recommended cutting President Reagan's defense budget $135.9 billion over the next five years to help revive the economy.

McNamara, Vance, Adm. Elmo R. Zumwalt Jr., who before retirement was chief of naval operations, and McGeorge Bundy, a Kennedy administration national security affairs adviser, said in a joint statement that the spending cut could be achieved without endangering national security.

They offered a long list of weapons they said could be safely canceled, including the B1 bomber, MX intercontinental ballistic missile and three Nimitz-class nuclear-powered aircraft carriers.

They would also slow up the Army's modernization program and stockpile less ammunition than Reagan has proposed.

The former government executives, besides recommending net reductions of $190.8 billion in budget authority and $135.9 billion in spending for fiscal 1984 through 1988, also assailed Reagan on policy grounds, stating that he was trying to prepare the nation to fight a "prolonged" nuclear war and buying enough aircraft carriers to enable the Navy to sail into the Soviets' back yard if war came.

This latest plea from former leaders to cut the defense budget came in the form of a 12-page paper to the chairmen of the Senate and House Budget committees. "The economic foundations of our national security, which are every bit as important as the defense component, have been undermined," the paper states in giving the rationale for defense cuts.

The United States, the paper continued, has "strayed in the direction of doing too much rather than too little" in national defense in light of the state of the economy and federal deficits projected to top $200 billion a year if not restrained.

Even after their proposed cuts, the McNamara-Vance group says, the Pentagon's budget would rise 5 percent a year even allowing for inflation, "which is as high as the growth rate has ever been except in times of open conflict. We believe it represents a level of effort that can achieve and maintain durable strength with durable public support."

In sifting through Reagan's five-year defense plan, McNamara, Vance, Zumwalt and Bundy agreed that there should be additions as well as subtractions, recommending in their paper that the 2.1 million men and women on active duty receive their scheduled 7.6 percent pay raise this October (Reagan would grant no raise); that more money and equipment go into the National Guard and Reserve units; that money earmarked to buy long-distance cargo planes be spent instead on high-speed cargo ships.

McNamara, in parting company with his successor, Defense Secretary Caspar W. Weinberger, on the question of how much for defense, joins former defense secretaries Harold Brown, who served under President Carter; James R. Schlesinger, who served under President Ford, and Melvin R. Laird, who served under President Nixon.

The latter four defense secretaries all warned in interviews with The Washington Post last year that the Reagan administration had started more projects than the nation would be willing to pay for later in this decade.

McNamara and Vance elaborated on their report yesterday during a luncheon at The Post and a news conference at the National Press Club.

McNamara, while acknowledging that Congress and the country now seem in the mood to cut the defense budget, said "my fear" is that the economy will improve over the next 60 to 90 days and "take the pressure off" even though such a short-term upturn would not have "a damn thing to do with the deficit" over the longer run.

He and the others are afraid that over the long term large deficits will prop up interest rates and prevent economic recovery. His other fear, he said, is that Congress "will cut a sexy object like the MX and leave it at that."

Vance, predicting that the MX will be canceled, warned against deploying an anti-ballistic-missile defense, saying that this would mean scrapping the arms control treaty which "is probably as important, if not the most important, of any in reducing the dangers of nuclear war."

The big spending cuts recommended by McNamara, Vance, Zumwalt and Bundy in a hit list for the five-year fiscal period of 1984-88:

* $31.9 billion by canceling the B1 bomber.

* $21.7 billion by buying enough ammunition to last 45 days in a war in Europe rather than the 90 days' supply Reagan is seeking.

* $18.3 billion by freezing the active-duty force at the fiscal 1983 level rather than expanding as planned.

* $14.9 billion by canceling the MX; $10.7 billion by forgoing purchases of F15 fighters to guard against attack by Soviet bombers; $5.8 billion by canceling three Nimitz-class carriers (Congress appropriated money for two of the three last year).

McNamara said much deeper cuts could be made without hurting national defense. Vance, in urging the defense reductions, said that, "From the standpoint of foreign policy and maintenance of our influence in the world, it's vitally important that we be perceived as wise enough and strong enough to take the necessary hard actions to put our economic house in order."