I am witness to an ECSB truck with a 3400 stall running a 234/236 .595/.598 112 LSA cam. And it runs WELL. And that is on a stock truck intake and stock 706 heads.

A 5.3L can handle a decent cam, but the supporting mods have to match with it. I would not go over a those duration numbers I listed above and I also would not go over .60X lift. The stock heads run a 61.15 CC size, so any head milling would have to be minimal if a .60X lift cam is gunna be run..cause you don't wanna experience PTV issues.