Washington political handicappers with some inside knowledge of discussions within the Reagan camp said yesterday that Caspar W. Weinberger apparently has his choice among the top jobs at defense, state or treasury. Some of these sources said they expected him to end up at the Pentagon.

One source said that Weinberger's selection for that job would mean that President-elect Ronald Reagan -- after blasting President Carter for doing too little, too late for the Pentagon -- intends to trim military spending after all in his battle against inflation.

But another source, closer to Reagan, pooh-poohed that theory. Weinberger is the front-runner for the Pentagon, he said, because the president-elect knows him intimately and thinks he would bring order to the world's biggest military establishment. Cutting the defense budget, this source insisted, is not in Reagan's master plan.

Another possibility for defense is President Ford's secretary of the Navy, J. William Middendorf II, whose prospects are dimming because of an image of eccentricity. Farther down the list are John Connally of Texas and Ford's secretary of the Air Force, Thomas C. Reed, whose lack of national recognition is being offset in part by his backing from Texas Gov. William P. Clements. Reed managed Clements' gubernatorial campaign.

Reagan may not reveal his choices for defense and other Cabinet jobs until he comes through Washington next week. He is scheduled to arrive Dec. 8.