Here's what it should be for a 51, but it's probably the same for yours.
PS of gas gauge dash unit goes to gas gauge tank unit.
DS of gas gauge dash unit goes to ign. switch.
Gas tank sending unit should have ground.
You can take a wire and connect one end to one of the screw holding down the sending unit and attach the other end to the body. Drill a small hole in the body next the tank where it won't show and tap in a small screw if you have too.
Cecil...........
