prime busta vs prime saku would be an incredible fight. i'd probably go with Saku via Decision.
prime shamrock vs prime bustamante would be another great fight. Busta's submission game is probably better than Shamrocks. Probably Shamrock via Decision or Busta via Submission in late rounds.
Gegard Mousasi- 25-2-1
"However great the kindness and the efficiency, in every hospital death there will be some cruel, squalid detail, something perhaps too small to be told but leaving terribly painful memories behind, arising out of the haste, the crowding, the impersonality of a place where every day people are dying among strangers"
Busta and Frank are so similar in skill set that this is a tough call. I think it would be an all out war that would leave us all really happy with whoever won. That being said I am going to go swinging on a Sack and say Frank. But it really could go either way.