Verify coil

Here is the deal.........Mopar ignitions draw coil current with engine stopped and key in "run." So "what I would expect" at the ballast is "same as battery" very close to 12--12.6 at "key side"

Coil + should be somewhere from 6--9v depending on type of coil. A "hotter" coil might show less than OEM because they draw more current

Coil neg should be quite low perhaps 1-1.5V