@ turn of the century

12 gauge double barrel dual hammers on top serial #370943,how old is it,will it be safe to shoot

It could be your fuel gauge or your sending unit or the wires connecting them . If you have dual tanks it could be the switch that changes tanks. The most likely culprit is the sending unit in the tank.

Most trucks with dual tanks only have fuel sensors in one tank.

I disagree with that as both of them have a float in them. It is possible there is corrosion to the float gauge on fuel pump. You can either replace fuel pump and gauge in tank or take old one out of fuel tank and clean up the crude in it.. I just did this to mine and it works now.. either way you have to drop tank or take off bed which I found was easier.

Rail gauge is the distance between the inner sides of the two parallel rails that make up a railway track. Sixty percent of the world's railways use a gauge of 4 ft 8½ in (1,435 mm), which is known as the standard or international gauge. Gauges wider than standard gauge are called broad gauge, those smaller are called narrow gauge. Some stretches of track are dual gauge, with three (or sometimes four) parallel rails in place of the usual two, to allow trains of two different gauges to share the same path.