['68OrangeSunshine]

For the record, my shelves are Black, on a '68 White Face. The original paint is fading, and it looks a lot like Zinc Chromate was the primer -- sort of a chartreuse color.
Zinc Chromate is standard in the aircraft industry as an anticorrosion primer on bare aluminum, but I cannot fathom why Fremont used it on my truck.
My Stepside has a VIN of 8Z123xxx which could be between late November '67 and early Feb '68.