FYI, I doubt Barry Holdwater would back Haig. By then his more moderate side had come out. Also, he didn't even back RR in '76, so I doubt he'd step up to tge plate in this situation.
Goldwater backed Ford in '76 for two reasons:
A). Gerald Ford was the incumbent president and Goldy reasoned (probably correctly) that the GOP would likely lose with Reagan; and
B). He and Ford were very close personal friends.
Ideology had little to nothing to do with his decision to endorse in '76. In '84, though, he probably would back H.W. (if he were to back anyone at all) again because he was the incumbent.