It doesn’t matter for the induction lead… place the red power lead on ground, black on coil or brown wire terminal on fuse box. Just set the timing on a Big Healey yesterday.. they are all originally Positive ground.
On the pertrox unit… somethings they don’t tell you… you have to use resistor spark plug leads.. Using stranded metal core wires will fry the amplifier unit. you should use their coil and remove the ballast resistor from the circuit. the pertronix coils are internally ballasted. if you use their coil and keep the OE external ballast the voltage signal to the amplifier will be insufficient for proper operation.. been there, done that!