I know perish likes to use an LS6 cam on all their boosted LS engines, but im not aware of the LS6 head use, either way LS-6 heads and cam are very cheap to come across.
The LS in that truck is a 6.0LSX fast intake, patriot heads$$$$$, and billet throttle body, and all sorts of other good, that thing should be a rocket! not to put him down just saying there is a lot left on the table.. Maybe the thing just isnt on much boost i dont see it posted anywere?