I think that, until PBF loses, the highest Pac can be in the P4P list is #2, but those lists are so goddamn subjective as to be almost useless. I find PBF's style every bit as impressive as I find Pac's, if not more so, so that has no bearing on where I would rank him.
If Pac moves to 135 and fights Casamayor (who's the biggest threat there), my money would be on Casamayor.