Not the number of grounds that's important. But the size of the cable, and the quality of the connections.
Thanks- the power is definitely going to the "BAT" terminal of the HEI, not the "Tach" terminal. I ordered an HEI kit from Summit that includes both the coil and module, and while it's on the way, I'll check that possible voltage drop issue tonight. I can always return the kit if I don't need it.You're jumping ahead of yourself again. You still need to be checking to ensure it's got power to the coil during cranking, and also that the power is at the correct terminal of the HEI.
Don't go buying all sorts of parts, and then find out you still have the same issue.