The HEI controls the current to the coil. As far as the coil was concerned, just a different way doing the same as the ballast resistor was doing.
Ballast resistors were about .6 - .7 ohms for points and 0.55 ohms for the coil with the Chrysler ECU. There's some thread where we got close to figuring out when the higher resistance ballasts came into use. Maybe with Lean burn or after lean burn.