GM HEI. The one good thing about the HEI as many of us have "thrown" them at our Mopars, is that the module itself has some sort of current control. They don't seem to be fussy at all about what kind of coil you use, or if you use a resistor/ ballast. I ran mine for an whole (hot summer), mostly as an experiment, with an OEM Mopar coil and NO ballast.