Yeah the LQ4 is your better bet being the bigger cubic inch, just punch it, stroke it and slap some ported OEM heads and an aggressive cam and you will be at 590hp on the motor easy. But dgregg is right....it takes a lot of cash to make that kind of N/A power to the wheels out of a 5.7L let alone a 5.3. Hell my LS1 would take another 3k(includes tuning and what not) to get to 500rwhp and I am making 425rwhp right now.
500 is doable but very expensive and has to be spec'ed right or else the motor wont hold up long. Now going Forced Induction is a whole other story. Boost makes these motors smile...so does spray
