Another Mopar Off My Bucket List - Barracuda Fastback

Yeah, that's the idea. If you get a spike in the voltage, the diode will snub it so the voltage going into the MSD box doesn't go too high.

I can't promise anything, I'd need to be under your hood with an oscilloscope to really know what's going on but my experience tells me that an over voltage occurs that kills the box.

Can you remember which pole you connected first? Plus or minus?