Thanks for the help, guys.
But, the mystery deepens. Before the new coil went on, I checked the existing wiring. On the + side of the coil, I have a 12v feed (a white wire) and then the +supply (red) to the electronic module. On the - side of the coil, I just have the -supply (black) to the module. Just three wires. Swinging in the breeze, I have four 'spare' wires. None of them have power when the key is out of the ignition or when the key is in the 'on' position. Couldn't tell what happened at crank as my arms are not that long...
So the two wires that were connected to the dearly departed ballast resistor are still not connected together. Car starts after a few seconds (reckon that's just the fuel getting to the cylinders rather than an electrical malfunction) and the car runs well. As it's the only 240Z I've been in, I don't know how well it runs compared to others.
Part of me (okay most of me) stays it runs, leave it alone. But the other part wonders what those other wires are and is there anymore life to squeeze from the mill.
Anyone want to satisfy my small part (actress/bishop, fnar, fnar...)?