I think that Rockefeller, even if he selects a conservative VP, would have a very hard time in the primaries against a Reagan challenge. If many Republicans thought *Ford* was insufficiently conservative (and enough thought so to almost get Reagan the nomination in OTL), you can imagine what they would think of Rockefeller. It is just possible that Reagan won't run: maybe Nancy convinces him the danger of assassination is too great; or maybe he doubts that the American people will be in the mood for four presidents in a little more than two years. But if Reagan does run, I have a hard time seeing Rockefeller getting the nomination. Even if he does (Reagan doesn't run, and conservative opponents of Rocky divide their votes among several weaker candidates) a right-wing third party could make things difficult for him in the general election. OTOH, the area where he would be weakest (the South) was one which went for Carter anyway (except Virginia). And he has a much better chance than Ford of carrying the state of New York. (No newspaper ever had the headline: ROCKY TO CITY: DROP DEAD...)
If he does somehow win both the primaries and the general election, he might at least please some conservatives on foreign policy:
"[Stu] Spencer, in a 2000 interview with the author, also described Rockefeller as 'the toughest anti-Communist I ever saw. Much more than Reagan, much more than Barry.' I said to him, 'Why?' He said, 'If you were a Rockefeller, wouldn't you be?'"
https://books.google.com/books?id=yjuOAwAAQBAJ&pg=PT649
Finally, my standard joke on this subject:
"1979: President Rockefeller found dead of a heart attack in the White House, with his aide Megan Marshack
https://en.wikipedia.org/wiki/Megan_Marshack 'by his side.'"
https://www.alternatehistory.com/forum/threads/president-rockefeller-scenario.398258/