I've been considering some exhaust work on mine. XR7-4.6 makes a good point about stainless steel. Most aftermarket exhaust systems are made from T409 stainless. But if you live in a salted-road state like me, it will rust. When the time comes, I will be looking for T304 stainless, which has a higher chromium content.
1996 Thunderbird LX (4.6), previous daily driver
1995 Mustang GT (5.0), daily driver
1995 GMC C2500 (5.7), alternate daily driver