toss up... mike tyson does better with people taller than him that he can make a tall target out of and who is not as vicious as him and marciano is shorter and closer to his height and is kinda cut from the same cloth as him atleast closer to it than tall style guys, marciano would prolly do better with tyson than bigger guys could. tyson's a better boxer and marciano has probably alot more stamina than him tho and could probably hang with tyson until he got tired im thinking... also i dont think tyson would be acting to vicious towards marciano because tyson never really fought someone as dangerous as marciano, and as similar to his style as rocky i dont think... rocky is honestly pretty dangerous even tho tyson is a way better boxer. the size thing doesnt really matter cuz if they met at a weight they would be the same size on Fight night really, so its a big toss up. Tyson maybe could have very much met his match with marciano honestly i wouldn't bet on the fight
This answer is a pick 'em. Both had iron chins and both had a huge amount of power (I personally feel that marciano may have been a bit stronger but we'll say even.)
Power- Even
Chins- Neither had Ali-level chins but both still had good ones. Even
Speed-Tyson
Heart/Stamina- Marciano
Tyson was an early on attacker who gassed out during rounds 4-5. Marciano was a stalker who would begin relentless power assaults that nobody could withstand.
If Marciano can't escape the early onslaught, Tyson KO2. If he can withstand it, then Marciano would win by knockout.
Tyson would've clear advantages in size, speed, quickness and skills. But we all know how Mike usually lost steam and got frustrated if he failed to end a fight after 5 rounds. With a guy like Rocky, who had incredible stamina and, yes, an iron chin, Tyson should try and knock Rocky out inside 5 rounds, otherwise, Marciano would rally and drill him in by the 10th round.
Tyson under 10
Maybe Marciano
15 rounds