if anything is gonna go on a stock LS block, its gonna be the rod bolts. upgrade the rod bolts and you should be safe to 8k (not 24/7, but for the most part thats the main thing that fails..., it doesnt have anything to do the the valve reliefs in the pistons. it's an interference motor, it'll smack the valves no matter how big the damn reliefs are if something lets go).