You never mentioned anything about re-gearing your front. Do you realize that both ratios have to match in order to use 4wd? You can (if your in a real money pickle) just regear the rear and keep the front as is but you would have to remove your front d-shaft, leaving you only with 2wd. I see people selling 8.8s all the time. I would try to find one that already has your 4.88s (and prob. a limited slip or other locker) and just bolt that in. Then spend the money you saved on re-gearing the front to match. Just my two cents.
This rear is welded so not exactly perfect but this is not that much more than re-gearing both your axles would cost you. http://lsjc.org/board/showthread.php...&highlight=8.8