My buddy has a 06 sierra with the 5.3 lm7 motor and at almost 200k it has lifter noise and will randomly drop oil pressure. We are planning on pulling it and rebuilding it with some upgrades or swapping in something else. However neither of us know where to start when it comes to parts for these engines so i thought id ask on here. He would like to be around 400 hp at the wheels. Thanks!