With no Watergate, Nixon's diplomatic breakthrough's with China and the Soviets; Ford is riding the front edge of the wave. It probably comes down to the state of the economy. The
Oil Crisis of 1973 might well be the campaign killer for Ford. Carter, with a narrow victory
*edit* I'll double-down on Carter over Ford. With Watergate, Ford's first days as President were his finest hours. He projected as a man of integrity, to a country desperately in need of that quality. By comparisson to Nixon, Agnew, Haldeman, Liddy, Erlichman, etal; Ford came across as the Eagle Scout he had been in his youth. Even with the big personal hit he took with Nixon's Pardon, Ford still had a ton of political and personal good will going into the election.
No Watergate, Ford still assumes the Veep role because of Agnew's shenanigans and by association, maybe a little more tarnish than we laid on him historically. Agnew's crimes were more within the realm of our expectations of political hacks, so the need for a transcendant hero is lessened. In that view, Ford would have been viewed more as a gray Republican apparatchik - a decent man, but nothing to get excited about.
The Oil Crisis and the extended Recession would have been a millstone around any Republican nominee's neck. Bill Clinton used James Carville's "It's the Economy stupid" concept to great effect in 1992. The same theory could have applied 16 years earlier.