Any kit you find on Ebay that isn't an ETS kit will be a mostly DIY project. They just include a core and some bends that you can fab up to work yourself. It's mostly crap.
Like I said, you either shell out some coin for the nice ETS setup, or you shell out coin for a custom job. Otherwise, you learn your own fabrication/welding skills and do it yourself nicely or try to cobble together some bends and eleventeen couplers that are bound to blow off. /ubbthreads/images/graemlins/hsugh.gif
My setup was a custom job done by Andre at PINAmotorsports. Click on the link in my sig to see just how big you can go, yet still retain AC. Brianawd has the same core and did a good job piecing it together himself, as well as keeping AC.
You can get a GVR4 specific exhaust system from Certified Muffler (CMPE) out of Florida. Garfield Wright, a member of this board, is a dealer for them.