Given how close the race for the Republican nomination was, isn't it possible that if he hadn't dropped Rockefeller, Ford may have lost the nomination to Reagan altogether?
In which case, Reagan may have lost to Carter in the general, and thus as a result not run again in 1980 (or not have gotten the nomination if he had run).
In which case, perhaps Bush gets the GOP nomination in 1980 and beats Carter.
It's always interesting to contemplate how things might have changed dramatically in the entire time line from one small change.
Good points, Eric, especially the one about how small things can have big ripple effects.
Still, I suspect that those who favored Reagan over Ford found Ford unacceptable because of what Ford did or didn't do as president, not because of who his running mate was. I doubt very much that dropping Rockefeller really appeased anybody who was already against Ford and gung-ho for Reagan. It's hard to imagine a Reagan 'true believer' saying, "Oh, I wanted Reagan, but now that Ford dropped Rockefeller, I'll vote for him in the primary." Yes, Rockefeller was an irritant for conservatives, but their complaints about Ford went far beyond that.