Crank Sensor

I expect that the internal diagram of the HEI chip is incomplete, and for understanding only. I expect it generates 5 V from the 12 V source (BATT+). I understand the purpose of the Bypass is to make it revert to "base timing". In that case, it ignores the "B4" spark advance signal coming back from the computer. Simply don't connect the bypass pin and it will run in base mode. The "5 V out" label looks wrong, should be "5 V in to enable advance".

The advance signal simply time shifts the 5 V reference signal, as shown. A very similar thing is done in Ford's EDIS module, termed the SAW signal. Read more on both on the megasquirt site.

The 8-pin HEI module is simplest to wire. Grab a GM "external coil" and cable that goes with it and a simple plug & play. Also steal the connector for the pickup. I also grabbed a knock sensor and module (my Holley Commander 950 can use that). Connect to your Mopar distributor, spin it and watch it spark the coil. Twist the pickup wires or you can get "positive feedback" or "self-excitation". Best to drill a hole in an old dist. cap and shine a timing light to see where the rotor is when it sparks. You have a 50:50 chance of getting polarity right for the pickup wires. The only pin you need on the 4-pin connector is the ref pin. You will see that TrailBeast doesn't use that connector. My Holley controller does (w/ GM adapter harness).

As mentioned, then send the 5 V Ref signal to your Mopar fuel controller, power it with 12 V, and see if it pulses the injectors as you spin the distributor. If so, you are about done.