Although they are viewed as the Boys from Bechtel, George P. Shultz and Caspar W. Weinberger have not always marched in lock step. In fact, Shultz has said privately that he believes that Weinberger eased President Reagan away from naming him secretary of state in 1981, informed sources say.

The two respect each other's strengths and attributes, having served together in the Nixon Cabinet and later at Bechtel. But they have not been the personal intimates nor even philosophic soul mates that many here believe them to be, according to sources who know both.

And they will now play out their roles as the administration's top two national security policy-makers against a backdrop that was sketched in part during the days of intrigue of the Reagan transition.

Shultz was being actively promoted for the secretary of state's job then by a number of prominent Republicans, among them former Federal Reserve Board chairman Arthur F. Burns and former defense secretary Melvin R. Laird, according to informed sources. Shultz was willing to take the job, they say, and those supporting him believed they had Reagan convinced.

But Shultz and some of his supporters believe that Weinberger was instrumental in turning his friend Reagan away from Shultz as secretary, according to these sources.

As they understand it, Weinberger passed the word that Shultz felt committed to stay in his job as president of Bechtel, where Weinberger was then also employed as a vice president, general counsel and a director.

Weinberger is also said to have suggested during the transition period that it might be unwise politically for the administration to appoint two senior Bechtel officials to top national security positions, being aware that he too was in line for a top administration job. The job Weinberger is said to have wanted most was secretary of state.

Shultz was also ready to take the job at State, had it been offered--and not until he received a telephone call from the president-elect did Shultz learn that Reagan was being told otherwise. As one of Shultz' allies tells it:

"Ronald Reagan calls George and says he has talked to what he called 'friends of yours' and that he understands that George feels he has a commitment to stay at Bechtel. Reagan goes on to say he hopes George can help him in other ways. And that is the end of it. George never had a chance to say no."

Shultz did not dispute that version when it was recounted to him earlier this year by a Washington Post reporter. "I was never invited to join the administration," he said. "And I never turned it down--I never had a chance to.

" . . . I loved it in Washington. I liked what I'm doing at Bechtel , and when people asked me about whether he wanted to come to Washington again that's what I'd respond. Nobody asked me to take any job."

He also said he did not know where Reagan would have gotten the view that he was unwilling to become secretary of state then, adding specifically: "I never discussed it with Cap."

A senior White House official confirmed that Reagan telephoned Shultz during the transition period and that the president-elect was of the opinion that Shultz felt he could not leave Bechtel at that time, and so did not discuss a Cabinet job with him. The official said he believes that by the time the president-elect telephoned Shultz during the transition, he had already made up his mind to nominate Alexander M. Haig Jr. as secretary of state, and Weinberger as secretary of defense.

Shultz discussed the matter in an interview last April, during which he also spoke of some of the defense secretary's professional attributes that he admires.

"Cap is a very stand-up type of guy," Shultz said. "He'll have a view, and it's clear-cut. And he has a backbone of steel. He's not a trimmer . . . . It's never a surprise to me that Cap speaks out . . . . He's something of a renaissance man. He has views on a lot of things. It's hard for him to learn to bite his tongue."

At no time during the interview did Shultz voice overt criticism of Weinberger. And the only indication of minor tension between them came in side comments, when Shultz' tone left the impression that the Weinberger style was not necessarily his. An example came when he noted dryly Weinberger's academician and Anglophile ways. "San Francisco, Cambridge and Harvard--that he likes," said Shultz. "And there's London and the countryside--that he likes too."

Shultz and Weinberger both proved adept during the Nixon years at winning quietly, by means of behind-the-scenes persistence. And in that sense, Shultz may well prove an able policy-making companion for Weinberger, who feuded with the prickly Haig, and is known by admirers and adversaries alike for strong opinions, though also an unfailingly polite and courteous manner with critics and the press corps. (Weinberger is on vacation, and a spokesman, Michael Burch, did not respond to questions on whether the secretary played a role in Reagan transition discussions concerning Shultz.)

White House officials say they believe that Shultz will also be more in tune than was his predecessor with national security affairs adviser William P. Clark's desire for a smooth process of making and implementing policy, with a minimum of friction. Clark played a key role in the departure of Haig.

Clark went to the State Department to meet with Haig after an article in The New York Times a week ago Tuesday referred in a headline to a "Haig-Clark feud." The article centered on disputes between the two during Reagan's trip to Europe; in fact, Haig became upset with a number of top White House officials on that trip about matters of policy and protocol.

It was during that meeting that Haig is said to have told Clark he was considering resigning. Haig had threatened to resign many times before, and on at least one occasion he was talked out of it by none other than Clark, who was then Haig's deputy secretary of state. But this time, Clark is said by an informed source to have suggested that he air his grievances directly with the president. When Haig met with Reagan Thursday morning, he reportedly stopped short of pressing his resignation on the president; but a day later, the president announced that he was accepting Haig's resignation.