Have you installed your own kit exhaust?

T304 Stainless turns a goldish color when heated....and T321 Stainless changes color too, T321 is the most Heat resilient form of stainless...it is also very strong tensile strength wise....therefore harder to bend...so the guy wasn't lying to you.

For a car such as yours....I would go with T304 stainless, Mandrel Bent, and I would get online and order a bunch of mandrel bends, find a exhaust website and get some hangers, find some Stainless Mufflers and then take the car and materials to a Competent Welding shop and have it all CUSTOM FIT and TiG welded...not MiG.

But thats just me.
Good Luck either way you go.
Nice Cuda.