Driving back to his hotel from a Republican rally in te Albert Thomas Convention Center Aug. 11, Ronald Reagan confided his concern about indisputable evidence of a widening breach between him and former President Ford and asked plaintively: How do we deal with it?

The question poses a central problem of Reagan's 1980 presidential campaign. If Ford himself decides not to run - a strong probability - and is determined to undermine Reagan's second full-fledged quest for the presidency, he could do great, conceivably irreparable damage. This would be particularly true if he tries to block Reagan in favor of somebody else - most likely George Bush, in the opinion of the Reagan camp.

Musing out loud, Reagan said the problem had to be confronted, and that he felt Ford himself was less responsible for the anti-Reagan campaign than "people around him." The next evening, in Dallas, with Ford sitting near him at a Texas fund-raising dinner (for Republican gubernatorial nominee William Clements), Reagan made his move.

Looking at Ford, he quoted President Carter's encomium in the inaugural address ("I want to thank [Ford] for all he has done to heal our land") and added his own graceful compliment: "Histroy will record that Gerald Ford healed our land and by his example reminded us that this nation deserves our love. Whether those words will terminate this latest in a century of Republican feuds, they place Reagan in an unassailable posture: Proud and sensitive, Reagan has made his peace offering without groveling or begging. But one cynical Ford Republican, listeninng to Reagan's newfound praise of the man he almost upset in 1976, asked: "Why didn't Reagan say that in 1976?" The Ford camp, including the former president, still fumes over what it considers Reagan's lukewarm post-convention support.

Reagan's appeal to let bygones be bygones followed leaks from the Ford camp that the former president's memorirs, due in bookshelt next spring, will blame Reagan for Ford's defeat. Ford cautious friends that he has not yet finished late chapters of his book dealing with the 1976 campaign, but insiders are sure that just such a rebuke was all but certain - at least until Dallas.

Some Ford intimates, including ex-White House aides Robert Hartmann and Dean Burch, agree that the drumbeat of undercurrent propaganda against Reagan does not come directly from Gerald Ford. Supporting that judgment was a curious incident last spring involving Ford's office.

After Carter turned down an invitation to make the dedication speech at the new Herbert Hoover Memorial Library at Stanford University, library officials - many of them Reaganities - invited Ford instead. Ford was carefully informed that Reagan would be there. The two had not met since the Kansas City shootout.

Ford's office gave a speedy answer: No. But one library official refused to accept that no. Ford himself, he speculated, might never have seen the invitation: send an agent to Ford and ask him personally. That was the course taken, and Ford then said yes, he would be delighted. They met at Stanford, but the ice was not broken.

No chances were taken in persuading Ford to appear twice with Reagan here in Texas for his close friend and former deputy defense secretary Bill Clements. Trailing in his campaign, Clements flew to California to put the arm on Ford. "Ford had to say yes," an insider told us, "but he wasn't exactly joyful."

Reagan and Ford have at least one more joint date: in California for Evelle Younger's uphill race for governor against Gov. Edmund G. (jerry) Brown. But the success of the Ford and Reagan Show here in turning out crowds and raising money is certain to generage other requests for joint Ford-Reagan campaign appreances. Whether Ford, having broken the ice here, plays a consenting role is uncertain.

Reagan handled the former president adroitly in Houston and Dallas. At a Clements breakfast Aug. 12, Reagan arrived early to greet Ford at the head table, grabbed both his hands and held on while cameras whirled.

For the 1980 nomination race, such tender treatment is essential. If Ford attacks Reagan - rather than merely supporting Bush of some not other Republican - Regan would not be the only casualty. Another victim would be the Republican Party. That was Reagan's coolly calculated message to Ford here: Don't break up the party before the campaign has even started.