Would it worthwhile to screw in as much timing it takes to make it detonate, then pull it back some? Seems like a light becomes pretty useless if the ignition is retarding on it's own at RPM.
I'm not up on the HEI as I should be. But, most any electronic device has a slew rate so I'm pretty sure every HEI has retard with RPM like any other. How much you can only learn by testing the entire system with a distributor machine. And then tune accordingly.