My thoughts start with a 6.0 lq4 or lq9, lq4 has flat top pistons which some say is better for boost as compared to the dished lq9 pistons, plenty of 5.3/6.0/6.2 making that much hp on stock internals really depends on how hard you are gonna drive it and how much boost. Leave the intake alone and put the money into the heads such as Mast motorsports ls heads if you can afford them. You could hypothetically run it without an intercooler to save money my dad has been running his whipple supercharged 5.3 suburban for........ about 6 or more years without an intercooler or any aftermarket injection i think it runs at 6-8lbs i would have to ask, meth injection is not needed i don't think unless its more track orientated.
Not an expert either just have done exhaustive amounts of research and asked my dad more questions than humanely possible but here is some ls engine info if needed
http://pirate4x4.com/tech/billavista/LSPrimer/Part1/ check out part 2 for truck stuff