Greetings,
I own a 73 dodge balboa, basically a 73 dodge cab with a fiberglass RV shell on the back. When trying to start, it's getting fuel but no spark. It does't turn over. It will only start when i take the starer wire that goes to the starter relay, and tap it to the bolt where the battery wire, etc. goes through. The problem with that is that A, it's not a good way to start the car, and B, the starter has trouble disengaging. Basically, an awful way to try to start. i've replaced the balast resister, starter relay, electric ignition control unit, spark plugs, plug wires, and coil. Any suggestions would be really awesome! I tried to upload a pic of what i was referencing with the starter relay....

 

Check the wires at the bulk head or fire wall may have corrosion. Or at lease find a wire diagram for a truck of same year.