I did a site search and did a google search but didnt find what Im looking for.
Did Ford use different color primers under the various color offerings on vintage Mustangs?
No, nothing I've read in Ford documents, books and references or heard from workers and managers at the plants would suggest that
To keep cost down the same series of primer products and coats were applied to all of the vintage Mustangs shot with enamel. Not sure what they did for the small number of early 64's shot with other types of paint but don't believe they were using different colored primers for different final colors either
