[VetteVet]

Well after some head scratching and looking at the diagrams, it would seem that the brown (rear lights) and the green ( dash light ) wires would give you what you want.
The orange wire is hot all the time as is the larger red wire.
When the light switch is out half way, the orange wire is powering the green wire and the brown wire but when the headlight switch is all the way out the orange wire only powers the brown rear lights wire and not the green dash lights wire. So it would seem that if you jumped the brown wire and green wire you would have power to the green wire in both positions.
Looking at the third picture of your headlight switch I', m wondering if the bottom two wires are the green dash light and the brown rear taillight wires and if they might not be switched around in the sockets. A continuity check on the two terminals would show how they were connected to the orange wire in relation to the switch position. This would have to be done with the battery unplugged to avoid damage to the meter.