It'd be a real tough fight for both men.
Liston at 6'1, 215lbs, 84" reach vs Lewis at 6'5, 245lbs, 84" reach.
Liston's jab, similar to what Mercer did, would provide a way for him to steer Lewis to where he wanted him for his own attack. Lewis would be looking to outbox Liston and wouldn't want to risk brawling too much with Liston due to Liston's power and good chin.
What would be interesting is to see how well Sonny does at cutting the ring off and would ultimately be the determining factor of who wins the fight. I see it going the distance, but who manages distance the best wins the fight. If Lewis can keep Sonny at the end of his punches and keep Sonny off of him he'll likely win a tough decision. If Sonny can get close to Lewis and let his hands go, he could likely grind out a hard fought decision.
The key would be who establishes their jab better. If Lewis can use his jab to keep Sonny off balance and at bay, he'll most likely keep the fight on the outside and would begin to drop hard right hands behind his jabs. If Liston can push Lewis back into the ropes and into the corners with his jab, he'll have a much easier time getting close to start unloading his brutal hooks and uppercuts on Lennox.
It'd be a very interesting fight and I can see either scenario.