I have one on my '73. The PO said it was a MAC. I sent it to Evans Performance (Cumming GA), and for $140, they are blasting and ceramic coating it gloss black. I had sanded it and used VHT's ($12/can) high-temp ceramic spray paint, but it would rust thru in a couple weeks. I thought the ceramic was a bargain, and they say I should get many years out of it.
Fabricator