msd ignition

What year is your car, and how many terminals on the ballast? You can carefully strip out some of the wiring, just trace it back to the ECU

What it amounts to is you have TWO wires coming out of the bulkhead connector. One is hot in run, "IGN 1" or "ignition run" and the other is hot in start, or "IGN 2". This is normally brown, and it's job was to provide hot power to the coil + during cranking.

Coming off all that is wiring leading off to the voltage regulator, alternator field, supply voltage to the ECU, and some smog doo-dads depending on year of car, and sometimes electric choke.