Mosley by an easy win.Not to mention he was 32-0 with 31 KO's. Mayweather would have ran and ran Mosley would have chased and chased an easily outgunned him and knocked him out. Remember Shane is the natural lightweight Floyd won a bronze in the featherweight division. So Shane would have an edge in size,also he is just as fast,and throws a helluva alot more punches.