Finally getting to it!!! 1970 Duster 340
Just went thru the dash gremlins myself. A PIA taking the dash instrument panel cluster in /out, so much easier with the dash bezel on the bench (remember the ground). It is easy to follow each circuit and power each receiver pin / circuit individually with 12volts. A combination of the new and old bulbs along with new and old plastic receivers were NFG.
before the dash panel goes back in, test the pins coming into for juice. I had a blown fuse on one. Designed in the 60's, the whole set up is pretty simple....not rocket surgery
good luck!