Also, the setup I used (got the install kit from C.U. Offroad) did not require a longer serpentine. It uses a double pulley on the alternator and a secondary belt for the compressor. It was pretty slick, but not cheap.
I got lucky when I installed my setup because Brad Kilby had swapped a Dodge magnum V-8 into his TJ a few years prior so had some custom brackets made. And he happened to still have one on the shelf. So mine is also driven off the alternator pulley.
On my 2.5 it was the same setup. So I never had to worry about the longer serpentine belt.