At least a few hundred. But this is heavily slanted towards recent decades where Marciano would struggle to get a single win at the high regional level. More like 50 or so pre 1960. Those 50(give or take) are mostly packed in the 30 years between 1915 and 1945. On the flipside there are under 5 guys who peaked before 1905 who would even have a punchers chance of beating Marciano. With the 4 I'm thinking of being Fitz, Goddard, Bob Armstrong and Peter Jackson. And these are all hypothetical peak versions.
The only Marciano fights I've watched so far are his two bouts with Walcott. From what I ascertained, Foreman and Liston would be stylistic nightmares for him.
After Marciano, quite a few. Liston Ali Frazier Foreman Holmes Tyson Holyfield Bowe Lewis Klitschko s
I highly doubt that, to be honest. Hate to be that guy, but a guy in the 180s—especially one who wasn't particularly fast—would have a very difficult time giving up 40+ pounds to modern heavyweights. At that size, he wouldn't even be competing in the heavyweight division today.
What if we take it down a level? What about guys like Ron Lyle or Pinklon Thomas or Mike Weaver? Ken Norton? What would happen if Gerry Cooney hit undefeated Rocky with a couple of left hooks to the ribs or the heart?
All of the 70s greats, Ali, Frazier, Foreman, Norton Many from the 90s, Lewis, Bowe, Holy, Tyson, He's struggle against Usyk, T Fury, probably even Kaybayel. A small fighter against the giants can sometimes work but the guys of the 70s who were teak tough athletes used to going rounds would demolish someone that small, he simply wouldn't size up well and his power and resistance would all dimish as the size factor comes into play. It's probably a better question as to what light heavy's could stand up against him and beat him.
No. Any puncher with modern training should get Jeffries out of there. And even if Jeffries is the most durable man on earth Marciano would shut him out. At least Fitz and Goddard have the historic power and Armstrong and Jackson the build or skills that could translate paired with modern training. Besides Jackson maybe these are tangible things. Jeffries doesn't have anything that suggests he'd be an elite fighter in another era. People claim that Jeffries win condition would be wearing people down but he couldn't weardown Tom Sharkey in 45 rounds and regardless the rules aren't giving him the rounds to try. Marciano couldn't be Marciano in any other era but he could have been a successful MW or HW. Jeffries's game and resume was too predicated on the 1800s. I believe by 1905 the best 175s and 160s all beat him. If you look at when the guys he beat accomplished the things they accomplished to become names that mattered its a big bubble.