The 87 Shelby Lancer cuts out like it has a bad HEP. The tach dies in sync with this cutout. I have tried the following with no success.

Replaced HEP with known good unit.
Replaced power module with known good unit.
Replaced coil with known good unit.
General inspection of cap and wires.

With the fact that the tach drops out simultaneously, should I be looking at the LM next? I had an alternator which caused a similar issue years ago. I don't have a scope to read the output though, so that's a problem.

Any and all suggestions welcome. I have to tomrrow and Friday to get this going. Monday starts a new school year...