Hei conversion Intermittent start?

273 gives excellent details. I didn't read that you tried my 1st suggestion of running a jumper from BATT+ direct to coil+. That would take your bulkhead, wiring, and key switch out of the equation.

One more little thing. When I was testing the 8-pin HEI in my slant, spinning the distributor by hand, I found that it could "self-excite" itself - the pickup wires saw the plug wire current, causing a positive feedback loop so it would spark fast continuously with the distributor not turning. This was when using long jumper wires from pickup to HEI module. If you use short pickup wires and twist them, should avoid such false pickup. In the GM system, the pickup wires are only ~2" long to the module. Some, (TrailBeast's photos) put the module way over on the firewall. Mopar did that too, so maybe no issue, but its design is different too.