The federal bureaucracy would get more miles per gallon if it had better-paid drivers and fewer passengers, according to the conservative think tank supplying the Reagan administration with various blueprints for the takeover and management of government.

That recommendation, from the prestigious Heritage Foundation, will be important in weeks ahead. Reason: Congress faces a March 16 action deadline on proposals to raise legislative, judicial and executive salaries. The increases, averaging just over 16 percent, were recommended by outgoing President Carter, with the endorsement of President Reagan.

If approve by Congress -- in a required recorded vote -- most members of the Senior Executive Service would get annual raises of about $7,500 per year. SES takes in nearly 8,000 career and political chiefs who manage operations in most federal agencies.

The pay plan, contained in Carter's final budget, would have the effect of raising the ceiling on career federal pay (now frozen at $50,112.50) to $61,600.

In a mammoth book, called Mandate for Leadership, the Foundation recommends Reagan impose a federal hiring freeze (he already has done it) and suggests he defrost top-level executive salaries that have been put on ice for years by a politically nervous Congress and White House. Both proposals are contained in a chapter written by James E. Hinish Jr. He is counsel to the Senate Republican Policy Committee. His byline is respected by the new GOP-dominated Senate and by the House, which has more Republicans and conservatives (who tend to oppose federal pay increases) than in any Congress in recent years.

Summing up his report on regulatory reform, Hinish wrote:

"If a new president wants a sure way of winning friends and influencing people in the bureaucracy, he would push for an end to the current pay freeze, while retaining the hiring freeze. Most bureaucrats are professional civil servants dedicated to doing a good job and trying to make the system work, rather than being partisan obstructionists against reform . . ."

The foundation report warns that "those in the top layers of the bureaucracy are angry and resentful at the (pay) freeze; many of the most skilled civil servants have opted for early retirement. Moreover, it will be difficult for the new administration to attract new blood if those most qualified to serve are not able to serve without severe financial sacrifice."

Most of the key second- and third-level political jobs in federal agencies are unfilled. This is due in large part, Reagan aides say, because the kind of people they want to run government say they simply can't afford to move to Washington and take significant pay cuts.

". . .For the sake of making regulatory reform a smoother enterprise, and alleviating the fears and misunderstandings of the civil servants whose ideas and energies will be needed to make reform succeed," the report says, "the president should, among his earliest acts, declare his support for undoing the wage freeze . . ."

If Congress buys that approach on a bipartisan basis -- and it will require new, strong signals of support from the White House -- some sort of top-level pay raise may be forthcoming. Although $50,000 a year sounds like a lot to the average American worker (and it is a lot) the fact is many of these senior-level government jobs require decision-makers who act in life-or-death, multimillion-dollar situations almost on a daily basis. The price tag for an executive pay raise is peanuts compared to the savings that will be made through Reagan's tough federal hiring policy.