Don't get me wrong. The 4.8 and 5.3 are no slouch. Plenty of power to be made with those motors. I was just stating that it's probably more cost effective to start with a bigger engine when the time comes to start chasing power. A larger engine will make more power at a lower r.p.m. where the truck needs it and still be able to turn enough r.p.m. to scream up top.
Check out engine masters and car craft. There is almost always a new article about building big power on the cheap with l.s. engines. I swapped an aluminum 5.7 into a Honda s2k for a customer from the u.a.e. using water/meth injection and a cam swap. He wanted a "sleeper". The plan was to go hunt lambos and Ferraris. That car is /was one of the fastest cars I've ever been in. And I spent a couple years building fast ass street cars.