[ford38v8]

Marv, original tanks were tern plated, which was a type of galvanizing, a lead/tin rustproofing. Over the years, the tern coating would gradually go away, and the natural thing happened with the tank being steel, they rusted. This is why the sealers were introduced. Today rust is even more of a problem due to alcohol laced fuel posing an attraction to moisture, and the old sealers are incompatible, so new formulations of sealer have been developed.

Sorry, I haven't heard of any "New" tanks having sealer, and why would there be sealer only on the bottom? Niether of these sounds right to me. Not doubting what you said, but you may have been taken for a ride on that "new" tank.