Bolt ons needed before H/C
Headers is a must. If your an auto your probably gonna need a converter, manual might need new clutch depending on how much power you plan on making. Gears to keep the cam in the sweet spot. ls6 intake if your not 01 or 02. Suspension stuff to plant the power, new rear end when yours breaks.
you don't necessarily need heads and cam for 400rw and mid 11's. just a good cam. do some research and you'll see what i'm talking about!! these ls1s are crazy strong motors out of the box, doesn't take much to wake them up.
I have over 400rwhp with a cam and bolt on's, no heads. I would skip the heasds for now and get a rear


