Fury once said he could beat both of them at the same time with one arm tied behind his back? I doubt that could happen. However I do think the could beat them with the use of both hands. Their punches would feel like tickles, a jab would knock one of them out and then God have mercy on the one that is left standing. Up to what weight level can these behemouths take on two fighters at a time? Middleweight perhaps?
Realistically, Fury would get beat down. He would have a hard time finding both guys who are much shorter and fleet of foot. Pac would tenderize his ribs. Floyd would just dance around and be a distraction.