About the light switch, yes I did splice both the pick and the black w/white tracer together and attached them at the light switch terminal. I didn't know where else to draw any electricity from for both wires individually.

On my rallye dash, the blue wire feeds the brake light, and the black wire feeds power to the voltage limiter. The gauge layout may be different from a B-body to an A-body, I don't know for sure. I can say that an early Barracuda rallye dash layout is different from mine. I also could not locate a rallye dash wiring diagram, and have posted on here as well as mymopars, but with no luck so far. I do have a copy of the printed circuit boards for the Duster/Valiant (and others too), which has helped a lot.

Do you need me to give you a rundown of the terminals and what I have connected to each one, maybe for one last check before we finally finish this?