David,
What you describe/observe regarding your original paint is correct: "It seems the tank was installed before the interior was painted". This is what I found on/in both my 54/55 Chev and GMC cabs.
Since "I am not going for a 100 point restoration, just close", do what suits your tastes/interests/pocketbook.
We use PPG DP epoxy primer (usually after using PPG cleaner and conditioner with abrasive pad) and then paint the entire tank (old or new) - since almost no one will ever know (at least within the next 30-50 years), it does not matter what is done.
The exterior color on the exterior filler-tube to the cab-body; and, the interior color on the exterior filler tube viewable inside the cab (I found this on my 54/55 GMC COE cab and on my 54 Chevrolet pickup cab). The interior color on the filler-tube on the fuel tank.
Last edited by tclederman; 11/05/2013 9:10 PM. Reason: clarified the filler "tubes" colors
