Personally I think Rocky would have beaten all 3, but which of these solid contenders do you think would give him the toughest test. I personally think Chuvalo.
If Oscar Bonevena fights the same style or same game plan that he did against Joe Frazier I think he would be my choice.
They all have a decent chance of winning honestly, I’d say it’s 50-50 for Quarry a tad less for Oscar and just a tad more less of a chance for Chuvalo. They would be his best wins bar Chuvalo if he pulled it off in my opinion.
Quarry would take advantage of Marciano's lack of speed, and sloppiness and counter punch him to death. Then again, Quarry couldn't handle Frazier's pace, which was comparable to Marciano's and he was also vulnerable to cuts (even moreso than Marciano)