alright the 4.8l is the same motor as the 5.3l, 6.0l, and 6.2l just being the smallest displacement version.. The fist place you should start is a set of Long tube headers and free flowing header-back exhaust. A less restrictive intake such as a Volant cold air intake.. you can manipulate torque to the rear wheels by changing the rear end.. you should have 3.42 gears you could step them up to a 3.73 and notice a big difference in power at the rear wheels
All of this combined could net you over 50hp to the rear wheels while increasing torque all the while
