Aside from eBay, Look in the classifieds on this site and in the Mustang parts F/S on other sites. You will also need an aftermarket midpipe or have one fabricated from behind your cats. A right-side muffler hanger and two rear exhaust tip hangers, and a GT takeoff rear bumper cover will complete the conversion. If you cannot find a GT takeoff catback any aftermarket catback that fits 99-04 GT models will work, assuming your vehicle is 1999 or newer.