500hp 5.7? Whats it take?

Just toss a nitrous kit on it. 150 shot will get you there easily and its affordable. Source a used wet kit from something and change what you need for your car. I picked up a used kit off of a Mustang for $300, a used progressive controller, and had it dyno tuned to make sure it doesnt go boom. For less than $1000, I went from 380rwhp to 520 rwhp and 625rwtq w/ my '09 5.7 VVT.