They would clash in the center of the ring and a great dust cloud would go up. Who would be the last man standing? Yes Marciano is 184 pounds compared to Chuvalo's 215 pounds, but Marciano would be the harder hitter and could likely take what Chuvalo can throw. I see Marciano wearing Chuvalo down. If the ref is humane and merciful, Marciano wins TKO via referee stoppage. If its Ruby Goldstein, Marciano UD and Chuvalo has several broken facial bones and fractures. But make no mistake about it, Marciano knows he's been in a tough fight.
Chuvalo would do better than Rex Layne whose soft midsection was punished until he wilted against Marciano. Marciano wins a decision in an entertaining hard fought battle.
Yes 16 fight, 189lbs Carmine Vingo. No opponents of Marciano sustained broken facial bones. Chuvalo was 30lbs heavier than Vingo and a lot more experienced,and no one dropped him.
I think the fact that he wouldn't go down (likely) makes it worse because it means taking an extended beating. I think Fraizer broke his eye socket and Marciano in 1 punch power is at least comparable to Fraizer. Walcott said in his opinion, he hit harder than Joe Louis in 1 punch. If thats true he'd also hit harder than Fraizer. Perhaps not as quickly or sharply, but Chuvalo would be wide open. Taking blow after blow after blow like that would leave him with damage. And, early in his career, Tyson fought cruiser sized opponents like Mark Spain. Tyson stopped him and quickly, but he didn't put him into a coma. I'm not saying Marciano hit harder than Tyson, but it would take considerable punching power to do that to a 185-190+ pound guy. Its the total damage that Chuvalo would likely take if the fight goes for the long haul, IMO. And as far as total punishment taken is concerned, I think Floyd Patterson would get off easier if he fought Marciano as compared to Chuvalo.
Eye sockets are thin and comparatively easy to fracture. Several fighters have been put into comas and some have died as the result of beatings, not all of them from big punchers. I'm not saying Marciano wasnt a hard hitter ,I'm just taking exception to your statement that he would fracture/break Chuvalo's facial bones when in 49 fight, against smaller men, he never accomplished it. On the flip side Marciano was cut and marked up in many fights against appreciably smaller men and in danger of being stopped in a few of them, he is going to ship some damage here himself!
I dont doubt that Marciano would find himself in a hard fight. I would be shocked if it did turn out to be an easy fight for Rocky. Maybe I should rephrase and say Chuvalo would take damage from a bad beating if the fight went the distance. But he'd give some back. My reasoning is the volume of hard punches that Rocky could consistently throw without letting up.