This would be a tremendous epic.
Frazier has been titeled as Black Marciano many times but I honestly believe that The Brockton Blockbuster was faster, more versatile, better chinned, more skilled, more elusive and pigger puncher.
Marciano would weather the storm early and finish George somewhere in rounds 8 to 10. The young (prime) Foreman didn't have a good stamina and was very voulnerable to infighting crisps, swinging wildly. Foreman didn't have that one punch skill.. cose he certainly had the power.. and Marciano would just hunt him down and step on him in the later rounds.
Just one Great I think Marciano could beat and look good while doing it
cheers