This would be a close fight and probably a boring fight. I would give the edge to Ali, by decision, but not by much. I think Tunney is very underrated.
Ali is better in every department outside bodywork... A thorough destruction with both being in their prime.
Someone will denounce Tunney "a stylistic turd" for prime Ali, in fact, Tunney is just a smaller prototype for Ali. Ali in a boring stoppage.
Tunney the greater technical fighter. Ali's physical gifts of incredible hand and foot speed however allow him to overwhelm Gene later in the bout. Ali by 15 round decision in a 10-5 fight.
I don't think Ali stops Tunney either. Ali's size advantage would assist him here...Tunney's great chin, survivalist smarts, and legs would enable him to see the final bell, as so many of Ali's opponents managed to do who were decidedly inferior to Gene. I agree with the 10-5 decision going to Ali. The thread starter is right about Tunney being underrated.