"Pulsing" voltage, RPM drop with load.

Here are some good articles relating to several electrical problems and upgrades to our older wiring ( near 50 + years old) and accessories, eg..gauges, charging systems, radios, etc...
Improved Wiring for older Mopars
Fixing Dim Or Blinking Headlights - Quick Tech - Mopar Muscle Magazine
Vintage Chrysler electrical repairs and updates
Vintage Chrysler electrical repairs and updates (part 2)