The voltage regulator in the instrument panel is for the gages. That's it. It opens and closes to provide the equivalent of roughly5 Volts to the fuel, temperature, and oil pressure gage if your car has one.
Reverse lights are switched on based on the gear selector position. If its an automatic with column shift, the switch was on the column. Floor shifters and manual shifters also have a switch but its not on the column.
Parking lights on a '67 Valiant are controlled through the 'headlight' switch.
Power from the main electrical junction goes to a fuse in the fusebox, then to the B2 terminal on the headlight switch.
With the switch one click out, power goes to the parking lights.
Two clicks out (headlights on) the parking lights go off but the rear lights stay on.
Follow the L8 wire from the main junction to the fusebox.
With no other info., I would look for wires with damaged insulation touching each other.
