h/c ? based on 2000ss's ?
Air Box Lid, K&N Filter, Smooth Bellows, Maf.. These will make small gains.
Bigger gains for Bolt on's.... Headers
Best power... All the above plus a head/ cam package... For streetability SLP's head cam package sounds good. They claim 445 HP, thats not rwhp though... A lot of the sponsors on this site have some good head cam packages..
Get yourself a set of stage 1 heads and a moderate cam............

