Engine Help Getting Started

I would think that the cheapest way to get good power would be to drop in a 94-95 302 and add a supercharger. You won't get to 500 rwhp, but it'll still give you a good kick in the pants when you floor it. But you can keep more of your existing V6 parts. If you really want over 500 rwhp, I'd do a Coyote motor swap. But you're looking at $15-$20k for a Coyote engine and all of the parts you need to swap in.

I wouldn't recommend a 4.6 engine, unless you get a DOHC 4.6. The SOHC ones in the 96-98 GT's have a bit less power than the 94-95 5.0, so you'd be paying more money for less power.

I swapped a 95 Cobra engine into my 94 V6, so you may want to read my build thread to get an idea of the work you have in front of you. The link is in my signature below.