Circuit diagram of Chrysler ECU

Not sure if I understand your question correctly, but...

At one time before ECU, the ballast resister would control the voltage / current to the coil (points)

Later with electronic ignitions there were 2 power feeds to the ignition. One was the power source for the ECU, the other was the power for the coil, a dual ballast resister fed each separately. (5 wire ECU)

A bit later the ECU was designed to run off of 12v directly. So only one ballast resister was needed for the coil. (4 wire ECU)

Pretty sure this does not answer your question but hope it sheds some light