Ali wins, by Decision. Make no mistake, ole Rocky was not one to get knocked out, and would be standing and trying his best until the end. He may get a knockdown, but he was too small and too slow to keep up
He was behind on the cards and well behind: 8-3-3 8-4-2 8-4-2 https://boxrec.com/wiki/index.php/Muhammad_Ali_vs._Joe_Frazier_(3rd_meeting)
Should add they both liked and respected one another. Rocky is relentless but the difference in length, weight, and speed becomes determinative.
Muhammad Ali belongs ahead of Rocky Marciano on any all time Heavyweight list. Head to head, Ali vs. Marciano, the situation's very foggy. No bets from me. I'll sit back and watch it, with many trips to my feet, I'm sure.