Fascinating question, actually. One guy clearly superior as a boxer and athlete, the other guy with a style that meshes with LPR to a "T". Ali is a far bigger, faster, and more durable Corbett with flimsy hands. Could end in a draw, with neither man able to land the finishing blow. With any sort of knuckle protection, Ali probably wins.
Gotta role with Fitz on this one. I really don't think Ali's suited to LPR between the hands and lack of an inside game, whereas Fitz is a great one with his pinpoint power punching.
LPR features throws and stuff. Ali was a great grabber, and I don't know if he's capable of translating that to effective throwing, even of a 160-pound man. I don't know if Fitzsimmons was a great thrower either. But I'll go with the bigger man. Ali wins. In the 56th round or something.