Horrific fight to call. Might depend upon what you stress, I don't think there will be much difference in terms of clean punching.
The Bodysnatcher would be cute enough to not fight Tiger's fight when possible. And when not, he would be rugged enough, to gut out the tough moments. McCallum WS15, in a neutral venue.
I think both could score wins in a series of fights. McCallum would be on the backfoot which was not when he was at his most comfortable. It would not be a wise idea for him to trade punches with Tiger consistently, which he realized against the younger and stronger James Toney. He could outwork Tiger and outmaneuver him at times but Tiger would be landing the heavier and more eye-catching blows I would think.
I can't see anything but a McCallum decision here. McCallum would outbox him from the outside with his jab and hold his own inside.