Plymouth Duster Instrument Cluster Wiring

Yep this later model doesn't have the large wires bolted onto the amp gauge like most of us have. Your model has a remote shunt somewhere and much smaller wires going to the amp gauge via the circuit board.
Brake warning lamp and oil warning lamp get switched 12 volts in and through them. Brake lamp ground happens at the hand brake switch and/or the switch on the proportion valve. Oil at the oil sender.