Reply to "Pertronix installation"

If you are determined to keep the ballast resistor and not bypass it, then I would suggest you go with a PI. They are a lot less prone to problems when running off less than 12v, and like the PII, they do not affect the tach operation. You will have to go with a lower output coil because a PI will not switch the high current level of a PII.

Back to my suggestion about bypassing the ballast resistor. I would not recommend running the PII level of bypassed current through the existing ignition circuit and switch if possible. You could hide a relay connected to the battery post on the starter solenoid and then use the ignition switch / ballast connections to operate the relay. This would un-load the ignition circuit and provide the PII the full voltage and current is needs operate under all conditions. You would then have a stock looking resistor and with wires, but the benefit of a modern ignition.

As far as differences between Mustang and Pantera ignition circuits, the Mustang did not use a ballast resistor. Instead it used a resistive wire like the latter Panteras. Physically different but electrically the same. The Tachs however are very different. The Mustang uses a current sensing tach in series with the ignition feed and is very sensitive to current changes with after market ignitions. The Pantera's Tach is Voltage sensing (more common) in parallel with the ignition circuit and is not upset, or worse destroyed, by more current passing through the coil.