According to what I read, right before he died, Sonny's management had agreed in principal to a fight with Chuvalo. George would have been 33, Liston, who knows, probably mid-forties? Sonny last fight was againt Wepnder. Even though he had slipped pretty far by then, I would go with Sonny by TKO. Liston's jab was always best avoided and George was not good at that.
Liston was still capable but not in his prime. One of my favourite Liston fights is Sonny vs Clark. He was still really good in thAt one. Chuvalo was a handful. This is the type of fight I want to see Liston in. George didn't beat great fighters but he could hang with anyone. Chuvalo could hang with Liston, I just dont think there was a point in Listons career where he had declined enough to convincingly lose to Chuvalo. Chuvalo vs Liston would always be a points fight if it was 1960 or 1970. It would answer a lot of questions for me about Sonny because this is a very physical fight against a game handful.
I'm going to side with George by 1970, Sonny still had the heavy jab but I don't think it would have kept Chuvalo at bay during the second half of a ten rounder and George was strong. If he could let his hands go a little he may have gotten Sonny in trouble by that year and enough to win a close decision.
Liston by that time was less than a sure thing so certainly I could see George via attrition getting to him late.
Cleveland Williams was as old and as far gone as Liston when Chuvalo beat him but because Liston was always better than Cleveland it's worth giving old Sonny the benefit here. To say Chuvalo beats Liston is like saying Sonny was never any better than Cleveland Williams. This is simply not true. Sonny was always better than Williams. He proved it twice.
Sonny Liston knocked out Zora Folley, George Chuvalo was out boxed by him. Liston knocks out Chuvalo any day. See what I did there?