hey, i have an 02 sixer and live near the steeda manufacturer shop. i bought their h pipe adapter for the six cylinder, and their gt true dual cat back set. it was pricey, around 700 for everything. i installed it all myself with wrenches and a saws all. it was not to bad. you just cut they y pipe a few inches back after the cats and then bolt the h pipe on. this h pipe system runs about a hundred bucks, and will allow you to use any dual exhaust system. you could buy this h pipe and use any exhaust system, but it is a great pipe and will not affect your cats. this adds a very deep good sound.
www.steeda.com i can answer many questions about this that i have not covered yet. feel free to contact me