Bill,
Your response interesting (and, all of it is reasonable).
One of the trucks I am restoring is an excellent-condition original-interior 1954 1/2 ton pickup and I was surprised to find that only the front/visible surfaces of the fuel tank was painted (the tank and the paint are in excellent condition. The color of the visible surfaces of the tank is the interior color. The cab behind the tank is the interior color - I could see no overspray around the fuel tank in the cab.
It looks like the visible surfaces of the fuel tank were painted with the tank outside of the truck?
Also, in my 1954/55 Suburban, and pickup, and GMC COE, there is no indication of that black primer was used on the interior surfaces.
Regarding all of the above observation, other years might be different, of course.
