Originally Posted by Matt Monson
A 304 SS header for these cars is a waste of money. The reason I say this is because when Cobb made theirs they did a lot of testing and found the thermal (heat retention) values of the mild steel were superior to stainless. Even though stainless has this reputation for being more durable and prettier it's not the best performer. It will be easier for you to hit a lower price point with mild steel, which will also give better performance than an identical design out of 304 SS.
In addition to matt's thinking, you could offer a SS and mild version of both. same jig, same bends, no extra tooling just different material.
One thing I would have paid for if it existed was a header heat shield, much like the factory one, to help heat retention AND insulate that annoying seweing machine sound of the valvetrain that virtually all aftermarket headers will allow.
If the factory SS exhaust manifold used one, a thinner aftermarket header, (especially one with longer primaries) would need one to maintain the heat that the factory setup called for.