I don't think Ray Kroc could beat either Nixon or Reagan/Ford in 1968/1976.
That said, he would be an interesting candidate if he got the nomination. He'd probably lose to Humphrey in 1968 (by the exact margin Nixon won by), and in 1976, since it would be much harder to tie him to Nixon than Ford was, he'd probably beat Jimmy Carter.
What do you think the maps would look like?
I'm not particularly good at doing maps for older election cycles, but I suspect that the main effect of Kroc getting the nomination in 1968 is that Wallace doesn't run, and Humphrey picks up some of those states, giving him the Presidency.
In 1976, I would guess that Kroc would spend his personal fortune to blitz Carter on air, and probably would flip Pennsylvania and Ohio, giving him the Presidency.