Riddle me this, Mopar electrical experts.......

Run a grounding loop picking up an attachment screw on voltage regulator, orange box, case of alternator, and negative battery terminal. All three of these devices have to be at same potential, and won’t perform correctly if not grounded properly.

As 67Dart273 said; check for good ground connections at block, and head to fire wall. After grounding system is good to go, look for broken wire, bad connection at bulkhead connector including connector crimps, and under dash splices. Examine fusible link for damage.

I suspect that where you were working in engine compartment, the problem will be found there. Chances are good at some point a wire got pinched, or pulled a bit too hard during the engine swap.

One more place to check would be reluctor and magnetic pickup for proper gap, and resistance.