Ground Question

I had a similar issue on my 74 Dart. Cleaned and re tightened firewall to motor ground( braided wire in engine compartment). Removed the 3 bottom screws for instrument cluster as they provide a grounding surface to metal frame of dash. Cleaned surfaces to ensure a proper ground and re secured with a slightly larger screw to ensure instrument cluster was tight against dash metal framing. My problem happened out of no where. One day it was fine and the next, everything was out. All lights work now after doing that. Good luck.