I would not recommend trying to coat the interior of the tank.  There are gas tank reseal kits, POR-15 makes a good one, but the Vanagon tank has an internal, non-removable strainer screen that will clog if you coat the tank.

On tanks where the screen is removable the reseal kits can work well, even on those you have to be careful of vent tubes, etc. and be sure to blow them out with compressed air before the sealer dries.  Don't ask how I know....

Allan

On Tue, 21 Apr 2009 12:24 -0600, "Warren Lail" <wklail@GMAIL.COM> wrote:
> Bill,
>
> No experience with Bus Depot's fuel tanks, but if you remove your
> tank, you can clean it with Muriatic Acid (be careful) to remove the
> scale.  Some people re-coat the inside with a polymer (I think).
> There may even be kits for this procedure.
>
> Best of luck,
>
> Warren in Santa Fe 88 Westy
>