could this be causing an issue?

Nope. No voltage regulator on the dash. and my truck is a '74

I would bet you money it DOES

I can bet money it does too, my 1979 does and yours has the same dash in it, its a 3 prong 5 volt regulator that sends on/off power to achive 5 volts

even our old A bodies have that, in your truck its behind the gauges on the printed circuit board

Found this wiring diagram for a 79 over at MyMopar

http://www.mymopar.com/downloads/79_Dodge_Truck_Wiring_Diagram.zip

In the drawing of the 79 cluster below, my horrid photo skills circled the 3 VL terminals. I think I got it right side up this time, LOL