The exhaust is built out of 409 stainless. It is ferritic, hence it has a fairly high amount of carbon in it. It will rust and a magnet will stick to it. Once it rust to a degree the corrosion will seal it from corroding any farther. Kind of like anodizing of aluminum. The exhaust is completely stainless ( except the manifolds ). If you think the exhaust is about to rust through take a screw driver to it. Push on the outer surface it should be solid and hard. If it has some flex to it, it is about to go. Probably from road salt... I built my exhaust from the cats back. Not the most frugal way but the most flow available other than replacing manifolds and cats. 2 1/2" out of the cats ( cut off 2 1/4 in tubing ) into a magnaflow "Y" and 3" out to the back. I used a Magnaflow muffler ( large case ) and mandrel bent stainless tubing all the way out to the back. It is noticeable but quiet going down the road... The factory exhaust is 2 3/4" from the "Y" to the resonator and back into the muffler. If you have the V8 I would get the Gibson exhaust kit for the 3" tubing diameter for a kit that either you or an exhaust shop could install. That would probably be the easiest route for most.
