Just went to a dealer and drove a new 1500 sportside, regular cab, 5.3, with trailering gear and 3.73's. Very stout...no way I would go with 3.42's now. I take back everything I said about mods. This rascal is too complex. I'd just get K&N and and 2200 stall 12 inch converter. The exhaust is huge like something for a 454, I'd just get a hi-flow muff of some kind. Probably the biggest boost would come from new programming like from hypertech to remove all the limits and constraints. I'd get pirrelli scorpion SUV tires and rear sway bar of some kind. Otherwise, its ready. A shift kit might help, as well as the full 1-2 and 3-4 servos. What might be causing some tranny problems is that chevy limits lubrication in overdrive and the shift kit restores that but it costs a little in miles per gallon.
juma, still thinking...