No earlier than Tyson. No later than Smith. He might have more trouble than people think along the way.
Marciano was a better fighter overall,but Bruno would have had a three stone plus weight advantage. If they were the same weight,then Marciano would have done it a la Mike Tyson.
on the suface, Frank Bruno sounds like a potentially easy opponent for the Rock, especially with his career long tendency to fold when under pressure against big punchers. As one poster mentioned however, Rocky probably isn't getting Frank out of there any earlier than Tyson did, and Bruno sure as hell had more than enough power to floor, stagger or stun Marciano. The funny thing is, Bruno would likely be both the largest and hardest hitting opponent that Marciano ever met, but the same can't be said in reverse. Frank took lot's of ferociously hard shots before finally folding in defeat. He also KO'd 38 of 40 victims and had Mike Tyson, Lennox, Lewis, Tim Witherspoon and oliver McCall rocked... I don't know.....
Bruno hit very, very hard and had a great jab. He was stronger and bigger than any foe Marciano faced. If Walcott KD'd him, Bruno might decapitate him. And if Marciano is willing to take two to deliver one, this would be a very short night. If Marciano could avoid absolute annihilation in the first 5 round he might have a chance. That said, I don't give him much of a chance.
Bruno hit verd hard, but I don't think his power shots will translate that bad against someone as small as Rocky. If Rocky doesn't try to slug it out with Bruno, I think he could pull off a decision. I wouldn't count on a KO. Although Bruno's chin isn't good for his size, he still carries far too much weight for me to even ascertain the idea that anyone with the mass and proportions of Rocky, no matter how strong or technically optimal their punch is can knock him out, unless he applies zero defense.
I understand the thinking behind the size issue with Rocky. I have to question how he would have fared against Lennox Lewis for example. I dont doubt however that he would have been absolute dynamite against the second teir of superheavyweights eg Bruno, Ramhan etc. That is a class where size would just have made you a bigger target.