I would never swap my 5.7 for an LS engine. If I was going to do a swap, it would be a 383 Vortec stroker. GM built the 350 (5.7 L ) for 35 years for a reason. If you want performance up grades for your Vortec, here is what I did to mine. I removed the throttle body and cut off the defuser plate from the bottom of the throttle plate, just be sure to cut the plastic plate with out removing the rivets that hold it to the steel plate. I removed the plastic vortex box from the air supply tube that is bolted to the top of the throttle body, and I caped off the hole with a ***** can. This give a straighter air flow to the throttle body. I installed a cold air filter. There is no need for a CAI system if you do this. I installed Summit shorty headers, and removed the factory muffler, then I added 2 old school glass packs and ran duel out the back. This removes restrictons from the exhaust system (flow masters are restrictive) Then I bought a Jet programmer and tuned my truck to max performance. ( a black bear tune will do better than the Jet tuner) Because I live in the deep south I put a 170 degree thermostat in my truck, but it is hot here most of the time, 70 degrees today. One of my co workers has a real nice 2013 crew cab with a 5.3 LS and I can just out run him. You can you tube the how 2s.
