The State Department and the Pentagon are tilting in opposite directions on the complex and politically delicate question of how to change the U.S. position at the strategic arms reduction talks (START) scheduled to resume in Geneva on June 8.

How their differences are resolved will determine how acceptable the new U.S. proposal is both to the Soviets and to moderates of both parties in Congress who last week voted money for the MX missile on condition that President Reagan takes specified steps on arms control.

A main internal debate is over what is called "throw-weight"--the total lifting power of intercontinental-range missiles and how much they can hurl at an opponent. The Soviets have a big edge in throw-weight.

In general, the Pentagon wants to emphasize throw-weight in a revised START proposal and demand sharp Soviet cuts leading to eventual equality. The State Department agrees that throw-weight is important but wants to place somewhat less emphasis on it.

State Department officials say they believe that there are other ways to equalize forces, that Moscow would balk if throw-weight emerges as a direct measure of rival arsenals, and that this would set back chances of an agreement. In some State Department offices there are signs reading: "Real Men Don't Need Throw-Weight."

Aside from security aspects of this debate, how the differences over throw-weight and other issues are resolved could have an important impact on Capitol Hill. A number of Democrats and moderate Republicans supported the MX missile in Congress last week in the expectation that the U.S. START proposal would be changed to make it more negotiable and to help both superpowers move toward less dangerous nuclear weapons than the 10-warhead MX and its Soviet counterparts.

Officials said they expect these differences, or at least some of them, to be resolved at a meeting with Reagan and the National Security Council scheduled for June 7. They acknowledged that the president undoubtedly will have to consider not just the strategic merits of the competing positions but the likely impact of his decision on the bipartisanship he has tried to build in Congress on arms issues.

Besides the debate over START, a more vague but potentially more explosive problem could be brewing for Reagan in West Germany, where there reportedly has been renewed interest in an informal and unauthorized plan worked out last year during a now famous "walk in the woods" by U.S. and Soviet negotiators at the other talks in Geneva on intermediate-range nuclear missiles in Europe.

That proposal would have eliminated Pershing II missiles that the United States is scheduled to begin deploying in West Germany in December and left only less controversial cruise missiles to be deployed in several western European countries. But it was rejected by both governments at the time and Reagan ruled it out again on Thursday.

However, former West German chancellor Helmut Schmidt said last week that he found the "walk in the woods" formula "totally acceptable." U.S. officials acknowledged that continued West German interest in the formula is potentially troublesome.

The Reagan administration agreed last month to alter its START proposal based on the recommendation of a bipartisan commission headed by retired Air Force Gen. Brent Scowcroft. It recommended what Reagan wanted most: deployment of 100 MX missiles. But it also called for development of a less threatening, small, single-warhead missile in the future and for changes in START that could lead to a shift by both sides to smaller missiles and enhance prospects for arms control.

The current U.S. START proposal, submitted a year ago, calls for both sides to reduce the number of individual missile warheads by about a third to 5,000 each and the number of land and submarine-based missiles to 850. The Soviets now have some 2,350 missiles and the United States some 1,600.

The proposal also includes sub-limits on the biggest Russian missiles--the SS17, 18 and 19--so that there could be only 210 of all three types combined. These sub-limits are an indirect limit on Soviet throw-weight.

The U.S. proposal, however, also has a second phase to be negotiated after an initial deal. This calls for much steeper cuts in Soviet throw-weight until both sides have equal amounts at a level somewhat below the current U.S. level.

There is now a possibility, however, that a new U.S. proposal will call for only one phase and in that case the Pentagon wants throw-weight equality emphasized right away. Pentagon officials also argue that restrictions on throw-weight are needed to limit the size and explosive power of warheads.

The Russian missiles now have about 2 1/2 times as much throw-weight collectively as the U.S. force (5.5 million kilograms versus 2 million kilograms). Many State Department experts believe that is too big a disparity to expect the Russians to agree to remove.

The State Department at this point favors retaining the existing sub-limits proposed for the biggest Russian missiles as an indirect measure of throw-weight, believing that may put a reasonable arms agreement within reach.

There seems general agreement that the 5,000-warhead ceiling should be retained. But there is argument over the 850-missile ceiling.

The State Department wants to increase it, reportedly to 1,100 to 1,200 missiles. This would make room for the small missiles recommended by the Scowcroft Commission, and it would also move closer to a Soviet proposal at START which calls for roughly 1,800 strategic missiles and bombers on both sides.

The Joint Chiefs of Staff, according to officials, favor keeping the 850-missile ceiling, believing that enough small missiles could be fit under it.

Civilian officials at the Pentagon tend to favor getting rid of the 850-missile limit and focusing instead on a combination of warheads and throw-weight. They argue that raising the level would erode the impact of President Reagan's pledge to seek very deep cuts in rival missile forces.