I know it's a long shot, but could Marv do it? Is there any way he could go up to 175 and beat Spinks? If not, how far do you reckon he could have gone if he had made the leap sometime during the early 80's? Could he have beaten the version of Hill that Hearns beat, for example?
As a LHW, Spinks was one of the best of all time. I have Hagler as the best MW of all time, but even then, going up 15lbs against a guy who was as good as Spinks was it a very hard assignment indeed! I'm a massive Hagler fan, but Spinks would prove too big, too strong! Spinks' credentials & skills were proven at the highest level!