Dude--just buy a 6.0L from somewhere. Internet, local junk yard, Craigslist...whatever. You could even buy a longblock with 317 casting heads. The exhaust manifolds, intake manifold, coil packs, accessories, etc..pretty much the upper end of the motor (sans the heads) of the 4.8L can be used on the 6.0L. Once you buy a 6.0L, MAKE SURE you tear that motor down and do a visual inspection of everything...like remove, clean, and inspect the intake, heads, etc. Go through it with a fine comb and a bunch of Brake Clean. Install new head gaskets when reinstalling the heads.

Modifying a motor is 10X easier when the motor is sitting on a crate on the garage floor versus being in the truck. If you wanna go all-motor, you should consider putting in a cam, valve springs, pushrods, 243 heads, pulleys, etc. before it goes in. Yes, a V8-to-V8 motor swap is pretty much a direct swap concerning the electrical hook ups, vacuum lines, TB, etc. If you installed a STS kit, you can swap a 4.8L to a 6.0L...