Foreman would gas because he was swinging non stop. His stamina is actually underrated. Tyson wouldn't survive those shots that stopped Iron chinned Frazier. He doesn't have the Chin and especially the heart to take those shots.
The best I can say is that I'd give Foreman a 55-45% chance of winning. I don't believe that it's a forgone conclusion that either fighter blasts out or even beats the other. Will Tyson's speed cause problems for Foreman? Maybe Would George be successful backing up Tyson? It think so, for as long as the fight lasted. Chins? I would say both have great chins. Tyson went through hell before being stopped by Lewis. Power, Foreman fairly clearly, but speed, Tyson also fairly clearly. i think the difference is that Foreman would be able to back up Tyson and Tyson wouldn't know how to deal with this. But I'm fairly sure that Tyson would bring more into the ring than Frazier did against Big George.
Now this is a reasonable and well balanced post, probably the first I've thus far read on the subject.
Ron Lyle actually had him down twice and in fairness was a decent hitter. Foreman came back to score the knockout in the fifth. One of the most entertaining heavyweight fights if you've never seen it. And yes Muhammad Ali and young each had him down once for a grand total of four times.
You forgot to mention the fact that both times Foreman was COMPLETELY gassed both times. You also forgot to mention that Foreman ALWAYS got up unlike Tyson.