Repeat HEI module failures are typically due to a failed ignition coil.
Module dies...replace it. Module dies again, replace it AND the ignition coil.
The GM HEI is "the" most-reliable OEM electronic ignition system on the planet. The first few years did have some reliability and performance (rpm) problems--select '74 vehicles, '75, and so forth until the in-cap coils got a black "ground" wire added, and the rotor color changed from black to white. I don't remember when that happened except I'm sure it was prior to '80.
I'm not saying the in-cap coils with the black "ground" wire are infallible; just that they're a better basic design than the ones without. The black wire is the "other end" of the secondary winding, which previously was connected to the primary winding; and still is on the stand-alone coils. The black rotors were known for "punch-through", where the spark would break-down the insulation and ground to the advance mechanism. GM first denied that that was a problem...then changed rotors to fix it.
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