I do remember reading about how Foreman, at the beginning of his comeback, contacted Holmes and asked him to fight some exhibitions. Holmes declined, saying that he didn't want to give George any heads up in case the two of them eventually met down the line.
Holmes by KO. I don't consider Holmes top 5 all time, or anything like that, but he had style and toughness to take Foreman to late rounds and Forman would fall apart, as he did agianst not just Ali, but Greg Peralta. Back then fights were still scheduled for 15, a distance Foreman could in no way last. It would be Foreman chasing Holmes, some exchanges, then Foreman getting tired and being picked apart. By 9 or 10 Holmes would put him away. So would some other heavyweight champs who could box.