I put in a new stainless steel system in 1990. All three pieces, the curved pipe down and back from the manifold as well as the silencer and the resonator (the small one at the rear) were all stainless. I had only a bit of a problem where the angle in the pipes between the 1st and the 2nd mufflers was not angled quite enough.
Never had a problem near the overdrive.
It's still like new after 18 summers of driving (98,000 miles). Before this, I only got about 15,000 miles and 3 years from every mild steel exhaust system that I used to buy from the S-T or British Leyland dealers between 1961 through 1969.