A low cab '36 might fit, the '37 tank fueled from inside the cab, and then you have the '38 tank. I believe that is all the tanks of this size, so it sounds like you all ready know what you have to do. I made a tank for my '37 that fit under the bed, but a good metal worker should be able to make something to fit under the seat. It may not look stock, but its a option.
joe
