I think that Nelson Rockefeller would probably win the election, but would have done much worse in the south than Richard Nixon did in RL, flipping several more states to George Wallace. In addition, I can see Scoop Jockson winning several states that Hubert Humphrey lost in RL due to increased vote splitting between Rockefeller and Wallace. Rockefeller would most likely have picked Senator Mark Hatfield of Oregon as his running-mate, while Scoop Jackson would have probably chose Congressman Wilbur Mills of Arkansas as his running-mate.
Here is what the map would look like:
Governor Nelson Rockefeller (R-NY)/Senator Mark Hatfield (R-OR): 274 Electoral VotesSenator Henry "Scoop" Jackson (D-WA)/Congressman Wilbur Mills (D-AR): 179 Electoral VotesGovernor George Wallace (AI-AL)/Former General Curtis LeMay (AI-CA): 85 Electoral Votes