Your regulator MUST be grounded right to "electrically the same" as battery neg. On most Mopars this was originally marginal.
The battery is grounded with the main cable to the block, which has a poor ground to the body/ "frame." Usually, a pigtail runs from the neg battery clamp to somewhere on the fender/ etc
I like to use a no 4 "starter" (ring to ring) cable. Your driver side cylinder head has unused holes in the back -- just look at the front of the pass. side, LOL.
Bolt about a 1 foot starter cable to the driver side rear of the head, and run over to say, the master cylinder bolt
You can also use a no 10 or s0 wire from the block over to the regulator mount.