Cranks but won't start. Unplug ground at field spade on Alternator and it starts?

Voltage test after I plugged bulkhead back in:

Battery: 12.4 volts at rest
Battery while cranking: 10.5 volts
Coil + side while cranking: 9 volts
Red bulkhead wire, inside car, at rest: 12.3 volts
Red bulkhead wire, inside car, cranking: 10.3 volts
Brown Ign 2 wire at bulkhead, inside car, cranking, 9.3 volts

All the above with Voltage Regulator and field wire connected, cranks, starter sounds very strong, no start, sounds like zero spark.