i would say that the 4.8L will more than surprise you. probably has more power than the stock engine that came with that truck.
My dad had one with a manual in it when i was a kid that thing rocked.
1999 GMC Sierra SLE ECSB .... 5.3L w/ Slight Performance Tune / True Duals with Flo Pro Glass Packs.
Project ''Bad Company'' Future = 6.0L (Forged Internals) / Boost (TVS) / 4L65E LvL 5 / AWD Conversion / Full LT's with Cats / Methanol Injection / Lowered 2" / SS Rims / Frame Up resto
Officially Employed!!!