Topic: When did Ford start using...

[Coralsnake]

Black primer for service sheet metal?

The earliest date I have found is 1980.

[Coralsnake]

After further digging I found a black primer part as early as 1974 and red ox as late as 1982

[Bob Gaines]

The red oxide have always been in the past perceived as more desirable at least on quarter panels for example because the later stamped black painted quarters suffered from the Ford stampings gradually wearing out and body lines not being as crisp. As your investigation points out that is not always the best indicator.

[J_Speegle]

After further digging I found a black primer part as early as 1974 and red ox as late as 1982

Did you record the stamping plant as well as the date for the panels in your survey? 

[Coralsnake]

I have a few pieces here and could do that....