The decisions, first Frazier would have lost on points in the Garden in 71 in their first encounter. Duran would have lost to Leonard in Montreal in their first fight. I have come to this conclusion after reading the skill set crowd wax on about "how its a boxing match and not a fight"...
Different rules, different fight strategies, different techniques, different outcomes. If John Jackson had fought under today's rules he would have been disqualified for holding Mendoza by the hair while he beat him.