I swapped a 06' TJ block into my XJ, because of the castings on the block the alternator had to be mounted in the TJ stock location. (same as in your picture) Currently running no A/C. I removed all of my A/C along with it (a/c condenser, hard lines, and pump) and i like the extra room behind the grille. I want to say it runs cooler (stays cooler)
The benefit of having the alternator up top is so you don't have to worry about water getting into it as much. But then you would have to get creative for OBA