Mopar dies when key is released

I didn't realize it ran in start, re: your PM

What you describe certainly sounds like "typical" bad ballast or loss of "ignition run."

With key in run, engine off, see if you have power on either side of ballast, or coil+, or at blue wire at alternator field. If not, you have a "switched ignition" or "ignition run" power failure, and a fuse/ link would be one thought.

Unless the later pickups have changed, that same buss supplies at the very least, the alternator blue field, the regulator ign terminal, and ignition run, and probably a few other things. The question, then, is "why" did it pop?

Is the wiring ragged? Anything been tapped into it (added?) Had any suspicions, as other odd behavior, intermittent charging system problems?