here's what I've found on 71Bs FWIW:

1. HEMI cars did still have black painted MCs (the black 10K mile HEMI runner is a good example)

2. My NOS disk brake MC has a gray phosphate lid with no writing and a metal tag with the 1176 number, a Mfr #, and PWR stamped on it. Date on the box is 72

3. I've only found one magazine road test from back in the day of a disk brake car that has a photo of the engine compartment showing the MC. It's a black and white photo, but the MC appears to be gray phosphate. Definitely not gold, and not painted black.

4. The FE5 SSP 383 car has what appears to be a gray phosphate lid. I don't recall if it had printing on it.

5. Every other "survivor" car I've seen has a gold lid. But these are not necessarily original owner cars...so who knows what's happened over the last 30+ years.

6. the MA article states that all MCs up through 74 were painted black. I believe that is NOT TRUE.