If modern American history could be made into a play, with exits and entrances and curtains that go up and down, the testimonial dinner David Rockefeller gave for Robert S. McNamara Thursday night would make a powerful scene.

They came, the men who had served as the country's informal council of elders for most of two decades, to pay tribute to one of their own who was retiring as president of the World Bank.

It was an extraordinary assemblage. It included two former secretaries of state, Cyrus R. Vance and William P. Rogers; old mules of the foreign policy establishment such as Clark Clifford, George Ball and McGeorge Bundy; industrialist Henry Ford, captains of industry and finance, former Cabinet officers and ambassadors.

But as they savored the bay scallops St. Jacques and sipped the Meursault Domaine Ropiteau 1977 at Manhattan's swank River Club, Rockefeller, chairman of Chase Manhattan Bank and the incarnation of the Eastern Establishment, sounded a somber warning.

It was time, he said, for a "blue-ribbon panel of diversified American opinion-makers to reassess the role of the United States in the world economy." It would be appropriate, he went on, to "reassess the nation's role in bilateral aid programs and in our dealings with multilateral agencies like the World Bank, the Export-Import Bank, the International Development Association and the regional development banks of Asia and Latin America."

Carefully couched though it was, there was no mistaking the message, according to several present.

The old order was changing, and the world that those present had worked so hard to construct was in danger of crumbling. McNamara was going in April. Rockefeller would be retiring in a few months. A new administration -- one in which the old guard's voice was muted -- had come to power in Washington. This was an administration that voiced grave doubts about foreign aid and the foreign policy system that had grown up around it. If the institutions were to be preserved, Rockefeller was saying, the time to rally behind them was at hand.

Both groups acknowledge that this shadow-boxing between the old guard and the new over foreign asd goes much deeper than mere budget cuts. At issue is the nation's whole approach to foreign policy.

As Democrats and Republicans, the men at the River Club had quibbled over the years on the details of American foreign policy, but seldom over the broad outlines. The policy was based on an enlightened partnership between Washington and Wall Street. On this there was agreement.

As U.S. banks and corporations built commercial bridges to markets and raw materials all over the world, the U.S. government build political bridges to foreign governments through foreign aid. There was Food for Peace, the Agency for International Development and numerous smaller agencies that channeled taxpayers' money into projects in distant countries.

U.S. government-backed economic development overseas was seen as contributing to political stability, economic growth and American influence. The giant banks and multinational companies benefited from this arrangement and, when necessary, provided the core of political support for it.

But radical conservatives now favor a sharp break with the past that would base aid to developing nations on U.S. self-interest, and would stress either bilateral aid or economic development by the private sector.

Conservative Jude Wanniski, expounding on the possibility of a "supply-side" foreign policy employing the same philosophy of tax cuts and private development being tried in the domestic U.S. economy, has called for a worldwide tax reform. Such a step would "free the energies of the people of the Third World in ways that would make it possible for them to eventually pay down their debts."

One administration officials said the policy shift on foreign assistance could involve "focusing our aid on countries that supply raw materials necessary for our defense."

The multilateral leading agencies find themselves at the center of the debate over the course of U.S. foreign policy and bearing the brunt of political criticism.

Business Week magazine recently described the World Bank that McNamara is leaving as a "demoralized organization, pilloried from right and left, looking for a role."

Critics on both side assert that the World Bank, the Inter-American Development Bank and the Asian Development Bank are, in effect, laundering operations that take money form U.S. taxpayers, mix it with funds from other countries and make it available for investment abroad with little accountability to Congress.

In calling on the Reagan administration to "deemphasize" the U.S. role in multilateral organizations, president Edwin J. Feulner Jr. of the conservative, Washington-based Heritage Foundation, has criticized the World Bank's loans to collective farms in Tanzania and Vietnam.

"If [the Tanzanians] want to try their little experimentation in so-called social progress, let them do it.

But I don't think they ought to ask American taxpayers to subsidize their Utopianism."

Countering these views, World Bank officials insist that international organizations played a major constructive role in the 1970s in easing the world through the transition to costly energy.They also scoff at the idea that the private sector can do this job.

Members of the Organization of Petroleum Exporting Countries now have billions of dollars on deposit in western banks. OPEC nations are unwilling to commit these funds to investments in the Third World, but the depositors are willing to commit at least some of these funds for development when the World Bank manages the investments and provides the guarantees.

Friends of the system note that only $1.5 billion of the annual U.S. economic aid of $6.5 billion goes through the international institutions and much of that money is spent in the United States through purchase of equipment or services.

In early skirmishes with administration budget-cutters, Secretary of State Alexander M. Haig Jr. won a commitment to honor all obligations to international organizations. This means however, that the United States will string out its $658 million payment to the World Bank over five years, instead of giving it in one lump this year.

Because the United States is providing only 7.5 percent of the Bank's new capital, the administration's plan probably won't impair its operations seriously, according to Bank Sources, though it could crimp the Bank's rate of lending.

However, administration officials say that after these prior obligations are fulfilled they will take a "hard look" at the U.S. role. And the first test of future policy could come soon -- U.S. commitments to one major leading institution, the Inter-American Development Bank, expire in 1983.

Meanwhile, the surfacing debate over foreign aid has revealed surprising areas of philosophical agreement between the left and the right of the U.S. political spectrum.

Writing in the February issue of The American Spectator, Wanniski launched an attack on "Eastern Establishment" multinational corporations and banks that could have been written by the liberal think tank, the Institute for Policy Studies.

He sharply criticized the Reagan-approved appointment of Bank of America president A. W. Clausen to succeed McNamara and charged that giant banks, fearful of bankruptcies in Third World countries, were behind the economic austerity programs devised by the IMF and World Bank.

And, in a radical departure from Republican thinking of earlier years, Heritage Foundation president Feulner argues that commercial banks went into the Third World countries "with their eyes open" and, if they made bad loans, they ought to be held accountable.