Reply to "Ballast Resistor"

I don't think that is completely accurate, at least for the Duraspark circuit.

While you don't want to limit the 12V feed to the duraspark module, you do need a 1.3 +/- ohm resistor at the coil to limit current going into it.

Google "duraspark wiring" and in every diagram you will see a resistor shown at the coil. Maybe some modern coils don't require the resistance in the "run" mode, but most of the older oil can style do.

Later L model cars feed the ignition through a resistance wire in the harness instead of the regular wire with the ballast resistor on the firewall the early cars used.

That resistance wire can be used as a pilot wire to throw an ignition relay to feed the duraspark module, but it doesn't supply enough juice to properly run the module on it's own. But, now you will have to add a ballast resistor to protect the coil.