I also see the evolution of the sport giving him troubles, but I think he could KO Hearns, and that he would turn into a brawler against Hearns much quicker then Leonard did.
I think him and Duran(this at WW) have a great fight on the inside, but Ray Robinson could hit so hard, I see him stopping Duran in the middle to late rounds.

Against Benitez I think he wins the same way he might agaisnt Mayweather, he would jsut overwhelm them with offensive, I don't see him landing enough to stop either but I see him winning these fights on aggressiveness(Similar to Berto-Forbes, but I see Robinson maybe landing even less against Benitez who is a defensive savant).