I think Byrd, definitely. But it's also worth pointing out that despite the fact that he was on the go from 1997 to 2007, there was always a behemoth that would have taken him. It's sort of the new normal. Roy, I would disagree unless you mean hypothetically. Or rather, I don't disagree, but I would never be of that opinion, because he only beat 1 heavy and it wasn't one capable of testing his fragility (like say Rocky...). Toney, possibly, if you buy that he was robbed versus Peter the first time but that's, you know, a bit of a reach IMO. I think Byrd gets ****-sticked a bit anyway. He could be the greatest non-great of the post-Tyson era, if that makes any sense. Hell of a question. I think he would beat a lot of the alphabet challengers. Keeping it with the guys who challenged for the legitimate title, he's obviously beating the Mike Dokes that challenged Bowe, he was 6'3 and 230-240. But even someone like old Foreman, who is listed at 6'3 and 250, it's very very hard for me to say he would "almost definitely" beat Old Foreman. That's because he's just walking in walking in. Famously Foreman said he tricked Moorer onto the right that brought him the title for the second time, famously Moorer hates him for saying it. Marciano - he just walks in and in, it's not about trickery. And yes, Marciano was probably tougher to hit than he looked on film, he was world champ, i'll buy that. But Old Foreman holds such a lot of punishment. That's such a long time NOT to get hit very hard by a big punch. I personally just don't believe, and think I am right in saying that it has never been proven, that a 185lb man can survive walking onto a punch from a 250lb bomber. I just am not convinced that that can happen, that it is possible. Physics. There's just not enough body through which to discharge that power. I mean a 230lb, it's not going to be easy or fun, but sixty five pounds is such a huge weight difference. I don't feel i'm denigrating Marciano, who I ranked #3 all time at the weight most recently, when I say it is very hard for him to beat men who are "on" when he is giving away a third of his bodyweight, a quarter of his bodyweight. Back to your question, I'd make him favourite over Ken Norton, because I feel he has a significant stylistic advantage over him. Norton was near-great to me, not quite top 20 all time material but nearly. Norton isn't quite as big as you specified though. Carnera probably isn't organised enough to beat him. I'd pick him over Carnera. What abour Razor Ruddock? Not in his prime in the way you describe, "almost definitely". How tall was Hasim Rahman? Rahman has probably only a puncher's chance. Is he six three? If so, that's my answer. Rahman once said he thought he would "fight a draw with Mr.Marciano." I thought that was respectful.
My problem with picking Marciano over the heavyweights that came after him (and I'm talking about the good hw's) is this....How does Rocky even reach them consistently enough to hurt them? A good big HW like Ali, Holmes and even the 1 hit wonder in Tokyo Douglas have substantial height and reach advantages over Rocky. Now couple that with greater hand and foot speed and a hard consistent jab and Rocky is definitely fighting uphill all night long. I liken it to a dive bomber attacking a tank. The bigger longer faster fighter can land from the outside while Rocky is constantly trying to avoid taking too much punishment while trying to get inside. I know intangibles play a role but there comes a point where size does matter..especially if it's coupled with ability. As much as I am a fan of Marciano, I just don't see a victory in the cards for him here.
We sanction former middleweights to fight guys the size of Douglas today, we just require them to get their body weight over 193 lbs by one means or another.
Until round 11 when in all likelihood Douglas hits the same psychological barrier as he had the last time he hit the career furthest round he reached in the other fight he was winning (against Tony Tucker) and crumbles. Pacing himself for the longer rounds won't provide the necessary sustained action required to keep Rocky off of him. Rocky hit harder than David Bey.
I think he troubles him with his jab, uppercut and right hand. I don't think Marciano establishes the proper range often enough to wear Douglas down before Douglas turns the trick on him.
I get the idea that you would pick any super heavyweight with a crumb of world class credibility, over Rocky Marciano.
Beating the most dominant heavy in recent history does not give one merely a crumb of world class credibility.
You picked Wilder over him before he beat Stiverne! Perhaps if we found a tramp off the street who weighed 230lbs, you might favor Marciano.
Pavarotti would have beaten him, because there are weight classes for a reason, and the fight would never be sanctioned today!