Right, so get an O/R h-pipe, which is only like $175. Shouldn't be that much when you are already looking at headers. Plus, not only for sound, but you would get more performance from catless or at least high-flow cats. In my opinion though - screw the ozone and 3 cheers for that muscle car sound!
Ok, but, i'm putting on long tube headers, not shorties. Hooker doesn't offer a H-pipe setup with their long tubes, but only an X-pipe (for around $250-$300). Thats why i'll cut the factory H-pipe down (cats) and expand them so the collectors will fit.
Go with the X-Pipe in theory the flow is unmatched with them. Check Granatelli motorsports out he has some Nice pieces for the 05-06 gt. header back all stainless 3" under 800 bucks