coil without ballst resistor?

A GM HEI module had both active dwell control and current limit, a ballast is not typically required. Current limit may differ, 5.5A stock, after market performance up to 7.5A. The active dwell adjusts coil charge to start, a few milliseconds prior to spark event. This greatly reduces heat dissipated (wasted) in coil. Points and Mopar ignition box need ballast to limit current, otherwise coils will overheat.

Using a 3.0 Ohm coil may reduce spark energy at higher RPM on a V8.

A scope and 0.1 Ohm 10W resistor can be used in series with ignition coil primary, to measure current by measuring voltage on resistor. One amp per 0.1 V. Viewing waveform will show current ramp as coil charges, current limit , and ignition event. Average voltage times ten, will be average coil primary current. Typical V8 points ignition draws about 3 to 5A, and can coils live at that. There are cheap lcd scopes for around $30.