Either Marciano swarm all over Fury behind his heavy punching on the body and head to take a decision in 15 rounds or Fury would out-box Marciano on the outside behind his long jabs and right hands to take a decision in 12 or 15 rounds.
Before I say anything I will say that the record of 49-0 will probably always stand in heavyweight history. Nobody cares if lighter weight guys go 50-0, cuz it's a record intended only for heavyweights.
Rocky Marciano will always be my favorite heavyweight but there are certain guys that Rocky would never be able to beat. For example, I don't think there is a heavyweight of the swarming style who could have ever defeated George Foreman it's just a stylistic nightmare for guys in the mold of Rocky Marciano.
That being said I've always maintained that it would have taken a guy with the conditioning and tenacity and perpetual motion attack of a Rocky Marciano to have the best shot of defeating Tyson Fury.
The problem is that there isn't anybody out there today who has that kind of conditioning or willingness to make it a dog fight to be as dangerous in the last round as you are in the first round--- but I tend to think that Rocky was just too small for Tyson Fury.
Don't get me wrong Fury will know he was in a fight because Marciano will hit anywhere and everywhere he can to make a dent, whether that be the gloves the forearms the elbows the hips, etc--- but I think Rocky would get chopped up and the fight gets stopped because of cuts.
Rocky could make himself an incredibly small target to hit, after all he could bend down practically touching the floor, but I think that would delay the inevitable. So I'm going to say that Rocky gets stopped maybe in eight rounds.