400 whp is a VERY lofty goal... doable but you're gonna have to spend alot of money. I would start with 9.5:1 pistons & L32 rods, and XP or perhaps even XPZ cam, GenV M90, and you should be good to run around a 3.2" pulley.. along with all the supporting mods (headers, intake, cold plugs etc)

If you want the simplest path to 400 wheel horseys, buy a turbo kit.