My Pertronix has a black wire and a black/white wire. The instruction leaflet says:
5. The black wire from the Ignitor must be connected to the ignition switch wire.
6. The black/white wire must be connected to the negative side of the coil.
There is what I can only assume is a ballast resistor, a white ceramic block with two screw terminals, which is screwed to the tub, and the black/white wire is actually wired to it, and thence to the coil.
I feel I am sort of too far down this road to turn back now, and I may have been less than perfectly prepared for the various tasks that arose, so I think I may go back to points so I can get it completed. I think there are at least a couple of sets of points in the parts boxes the PO passed on to me, will have to hunt. Otherwise it's a call to somebody and an overnight delivery, I guess.