Jack, I can tell you that the sloshing compounds available today for cleaning and sealing a fuel tank actually work. I did that with my '56 Cadillac 20 years ago and it hasn't leaked, flaked, peeled off, or anything. New tanks weren't available then and mine didn't have holes in it so I figured what the heck? Look into it.
I don't remember what product I used - it was probably Eastwood's. All I remember is the final coating was blue. No rust or leaks 20 years later.
The local radiator repair shop here will boil out your gas tank, too and seal it.. Maybe you could have yours cleaned up and repaired by a radiator shop or just boiled out. The you could apply the sealing compound yourself.
