Definitely clean your bulkhead connector...all connections. I like to use de-oxit. You should also clean the main connectors under the steering column. Lastly I would be certain to check & clean the two connections at back of amp gauge.

de-oxit

70 Road Runner 383-4 4 speed FJ5 & black guts
70 Charger R/T 440-4 4 speed FJ5 & white guts