Random HEI shut off
HOT WIRE direct to the HEI and see if it quits. If not it is the car harness and not the ignition. If it is the HEI quitting, you basically have three choices...the module, the pickup, or the coil.
I built myself an "emergency" HEI which also helps me to fire up old engines, occasionally, AND TO troubleshoot, as I can clip it in and eliminate components
I can
...Hot wire it in, which eliminates the car harness AND everything except the distributor. You can put clip leads into the pickup connector and clip it to the HEI pickup coil. You can "de wire" the coil and hook the emergency module to the present coil to test it
Green wire is ground, Yellow is power connection. No ballast