Electric issue?

How do you even know it's electrical?

Do you have a tach on the car? Does it normally indicate when cranking? If so you should be able to see if the tach does or does not indicate, cranking, when the problem exists (Some tachs are wired such that they go dead in crank so may not be the case)

I would "'rig" a small LED/other pilot lamp onto the power coming to the ballast. Pull the ECU off clean and remount, make CERTAIN the ECU is grounded. Pull all ignition system connectors and "work" them in/ out to scrub the terminals, and inspect them. The ECU, the distributor, and the ballast.

Another thing you can try is IMMEDIATELY when it dies, don't do anything, don't recrank, etc go out and --with key still in "run" check for power to ECU, and then pull the distributor connector. Take the ECU half of the connector (not the dist end) and tap the bare side of the connector to ground. Using the coil wire, look for spark. It should make one single "snap" spark every time you ground it