Engine Probs?

Both. The vacuum advance could mean that you have the advance hooked up wrong (normally "ported" vactuum to the distributor, which means NO vacuum at idle) or it could mean you have the timing set way too far ahead OR it could ALSO mean that the reluctor gap is wrong in the distributor.

Trying to run the car at only 12V won't do much good, either. Normal "running" voltage while the alternator is operating should be 13.5--14.2 or so, +/- a little

Also, some variations of Mopar ECU's do NOT like getting wet, if it's out in the weather. I used to have that problem with one in my 340 powered FJ-40