I got Spinks. I never really thought much of Shannon. Cooney was another big clumsy guy like Briggs that could punch hard but that's about it. Spinks took him apart and would likely do the same to big mouth Briggs.
Spinks takes apart a one dimensional Briggs with relative ease. Of course if Spinks gets careless and Briggs lands big, he could get Spinks in trouble. Spinks had a great light heavyweight chin but not a great heavyweight chin. Still I don't think Spinks gets careless.
Now THIS is a winnable fight for Spinks at heavyweight. He beats the crap outta Briggs. Shannon was a BUM! Always was. Complete trash fighter. The guy got his ass kicked from pillar to post by Botha. Spinks TKO 9.