David,
I can not be certain that the wiring in your beautiful white GT5 is the same as the wiring in the earlier cars.
Assuming it is......
The orange wire is supposed to connect to tab #1 of the headlight switch. The orange wire runs from the light switch to the fuse box, splits to fuses #3 & #4, and those 2 fuses supply the running lamps, rear tail lamps, side marker lamps, license plate lamps plus the instrument & control illumination for the dahsboard.
Your friend on the DTBB
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