Continue to troubleshoot or start from scratch?

I've been working on my 1974 Dodge Dart Swinger since buying it non-running last October. It was a slant 6 but the previous-previous owner swapped in a 360. As far as I can tell he never finished the project, so it's never run. We've got all the pieces and were ready to see if she would start. Got a new battery, hooked it up and tested a few circuits, headlights check, horn check, brake lights check, oil pressure dummy light check, so far so good. I decided to give it a kick just to see if we had cranking power. Nothing. I'm able to short the starter relay and it cranks. But I started to check for voltage at the coil, 3 volts. Ballast resistor got real hot real fast so I shut off the power. Started checking for shorts and ground. Seem like everything is shorted to ground, both coil wires, all the pins on the electronic ignition module, the ballast resistor, both field wires on the alternator, seems like every wire and connection I check is grounded/shorted. Damn, I don't even know where to start. Looking closer at the wiring, there are a number of plugs not connected to anything all go straight to ground. Question is, should I keep troubleshooting or start from scratch and replace the harness?