The crud flaking on the inside of the tank is probably an accumulation of old fuel deposits. Ethanol blend of fuel will break this stuff down and it reeks havoc on everything downstream of the tank. When the regular leaded gas was used back in the day, all of that stuff stayed put on the side of the tank.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission