Hi cyates219:
From my wiring diagram, this is how I see the power delivered to the circuits in question:
Red wire (12 RED-2A) comes from the firewall connector to the main power splice (splice-2) with a whole bunch of red 12 gauge wires in it...this should be near the fuse block. Then one red wire (12 RED-2B) goes from the splice-2 to the back of the fuse panel and supplies power to three fuses in a row: (1) ACCESSORY, (2) TAIL, STOP, CTSYLAMPS, (3) TRAFFIC HAZARD. The middle fuse, (2), is a 20A and this is what orange wire 18 ORN-40A is connected to and runs to the back of the headlight switch. It is spliced at this location to wire 18 ORN-40B which runs to the courtesy lamp under the dash. The right hand fuse, (1), is a 20A and this is what orange wire 18 ORN-140 is connected to and runs to the dome/cargo lamp. The left hand fuse, (3), is a 15A and this is also a orange wire, confusingly identified as 18 ORN-140, and this wire should run to your brake light switch located on your brake pedal arm somewhere.
I have a spare headlight switch squirrelled away somewhere and if I can find it I can let you know where the white and orange wires from this light circuit are supposed to plug into...I should be able to take a photo of it.
Regards,
Henry
1976 C-20 Custom Deluxe