Tough to pick against Floyd because he's so much better, but I'd go with the size and speed of Norris here.
I think Mayweather. He's smarter then Terry and I think he'd make the adjustments to take a split decision.
Probably It's hard to say, though, I think Floyd and Pac above 140 have been the beneficiaries of the worst welterweight division I have ever seen and Floyd has had only one fight (so far, though it will change) at 154 against an old guy and he was not all that impressive in winning an otherwise clear decision. For name value, he'd obviously be Norris's greatest opponent, but I am still not sold on the 147 Floyd, never mind the Junior Middleweight version.