Well welding is beyond me on either. There's a race shop in Norman that's doing the fitting/cutting/welding. Homemade is accurate because he's working out of my garage.

I asked him about the headers. He said they are cold-rolled mild steel, and yes the coating will keep them clean looking... and corrosion resistance (not proofing) is the only major difference between the two steels. The coating is inside and out. Stainless will turn dark brown after a while and look far worse than coated mild steel... and then if you end up coating the stainless for aesthetics, you've basically spent more on stainless for nothing.