A radiator repair shop cleaned, inspected and did a minor repair with solder on one my trucks tanks a few years ago. The charge was only $60. Had that not worked the tank was going to be replaced, as others suggested. I've read elsewhere that using the various in-tank sealers can lead to other headaches down the road. IMO I'd prefer to shave the odds against enjoying a plugged fuel filter or fuel pump at the (usually) worst possible time.
