You can literally swap in any of the ls series engines and it will run nearly perfect. you can take a 5.3 and swap it in and really don't even have to mess with the computer.
Cam, springs, possibly rockers, timing chain, oil pump.. Better to do all the stuff while you're there. Also a tune... Before you go pay hundreds for a tune, get ahold of me and i can have your truck tuned for 200 bucks.