I know this sounds crazy, but I actually think that this may end up being a mismatch.. Paul Williams has many similarities to Thomas Hearns, only he simply is not as good, and certainly not to the extent that it would take to give Leonard the type of battle(s) that Tommy gave him.. Williams has a problem with fast technicians, and what's worse, Leonard is a sweet scientist who can actually punch as well as out move and out think his opponents.. Bad matchup for Williams..
Leonard would be at his showboatng best against a guy as sloppy as Williams. PW's connect rate rarely exceeds 24% in a given round. He'd be at less than 10% against SRL. Ray by KO, as soon as he gets tired of clowning, and decides to close the show.
To balance things up you are putting in an absolute peak Leonard ? :huh Anyway... Leonard by knockout.
Williams is a good fighter with a good chin, excellent stamina and when he commits, a decent enough punch. ...Leonard by KO round 6. Williams also gives away most of his physical advantages in height and reach and goes head first into trouble. In a way, it's kind of endearingly unwise. I like the guy but these are not flaws you can get away with in a fight with Sergio Martinez, let alone Ray Leonard. Hey, where's RedRooster to tell us he has no faith in Leonard as a fighter and Paul Williams would beat the shite out of him?
Williams has no defense, doesnt use his height to his advantage and would be easily hit and knocked out by a sharp shooter like Leonard.