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.
Our Rancho Drivetrain trans is amazing to drive anywhere. We started with just their valve body but by the time we dealt with all the details we went right to RDE and paid way more than we wanted to for the Rancho trans build and it was worth all of it. It's worth talking to them. There are crappy valve bodies out there for sure.