If Ford could only just barely manage to defeat Reagan in 1976 as an incumbent with the full support of both the centrist & Rockefeller wings of the party behind him, then I have to imagine that he'd lose a rematch that would see those wings split among him & the likes of Poppy Bush & John Anderson.
Now, the more interesting question is whether or not Ford "pulling a Grover Cleveland" would lead the nominated Reagan to actually go ahead & choose Ford as his VP in this scenario so as to unite the party?
I’d imagine that many, if not all, of Reagan’s 1980 primary opponents wouldn’t have run had Ford “pulled a Grover Cleveland”. Poppy Bush definitely wouldn’t run, and I’d imagine there’d be a desire to consolidate the anti-Reagan vote.
Still, even if all of the anti-Reagan candidates unified around Ford, I'm not sure even
that would be enough: remember, Reagan had already almost beaten Ford when the latter wielded the not-so-insignificant advantage that was serving as the incumbent President of the United States. By 1980, with Ford not being President, Reagan could easily blame Ford for all of the problems facing America since it had been him who lost to Carter. (That is, campaigning on a message along the lines of "President Ford already had a chance to stop Jimmy Carter, & he lost. We're at least partly in this mess because of President Ford, so it's time for somebody new for a change.")
