Wish I had some I could sell ya, I have a pair for the 03-04 GT.. Best bets to probably get it from AM with a discount code. Most people that get the Borlas on the cobra never give them up, but there are a few floating around..
I know Lethal Performance is offering them for a little cheaper with free shipping, AM can probably match it and/or offer a discount, ive never had to do that or try however.
Amazon has them for 659 with free shipping. If that's too much watch them because they periodically have them used under their warehouse deals. That's how I got mine for my Mach 1. They were marked used but they were new but the box had been opened. I got them for 445 I think. Here's the link for the cobra ones. Still a heck of a lot cheaper than AM. I think they want 790.
They sound amazing with kooks 1"3/4 longtubes and an o/r x pipe. I polished mine. I couldn't be happier with the sound and quality. Got mine used on Ebay for $500.