Oh the joys of a rusty tank.
On your daily driver, you need to add another finer (smaller pore size) filter after the stock one. Or drop your tank and clean it. Its not good for the valves to have them seating on the fine rust and apparently its working its way there.
On the '61 you need to coat the inside of the tank or bite the bullet and spent the $ for a new tank (less than $200). From what I've read tumbling the tank doesn't work and I've heard mixed comments about the coating. I personally put new in all mine as part of the restoration. I don't like fuel problems.
