The absolute prime...let's say Rahman II Lewis....hmmm. I don't see that Lewis as being as mobile or deft as 60s Ali, and he had a far less durable chin. I can see him rocking the hell out of Sonny and frustrating him with his greater speed, but I daresay Liston hit harder than Mercer, Tua, Rahman, and McCall (and better than a way-past-it-Tyson), and he was just a plain better overall boxer. Lennox was a sensational fighter, but I see him getting stopped. I feel the same way about prime Mike Tyson, whom I also think would have dispatched of prime Lewis. That said, I do have LL at #6 on my list of ATGs...
No, Lewis puts that overrated can crusher into the decorticate posture with that big right hand. Lewis by savage KO.
McCall was good enough to be World Class in a tough era. He also likely had the very best known chin in boxing history. Fought forever, big modern guys, 300 + rounds with Tyson, the "Atomic Bull" was no defensive genius so logically if he is never even knocked down, he is a prime candidate for GOAT beard. None of that means he is likely to beat Liston. Who was clearly better overall, & there is no stylistic advantage to say maybe Olliver wins. Liston easy decision.
McCall was strong, iron chinned and a decently hard puncher. I'd favor the best McCall over the best C. Williams. But ultimately, I think Liston batters him