I need to know where to locate a fuel sending for my truck. I have a '73 D200. The fuel gauge is stock. The stock tank was just behind the cab on the driver's side. It was outside the frame. It is been removed and a different tank has been added. It is long and narrow. It is between the driveshaft and frame. A hole was cut in the side of the body and a fill tube was placed there. My gas gauge does not work. I do not know if it is the unit, gauge, or something in between. If it is the sender, where do I look for a replacement other than buying a unit and matching gauge (ohms) from Summit, Jeg's, etc.?