[C. Ludwig]

I always send them all to the rotor housing or head. It's convenient and works. Basically, two of the grounds are kind of along for the ride and won't influence performance. The high current (Pin D) is the one you need to have well sorted. If the block ground is marginal, (which it should not be!) then go to the battery. Better yet, ensure you have good grounding of the block to the battery negative post and then ground all 3 pins of the coil to the block.