I've contemplated doing this to the B as the low beam headlights are candles, really small ones. I don't run the high beams much as I know the old switch won't handle it as I put Halogens in it.
I'm thinking of just using the actual headlight power wire(from dash) to run the relay at each headlight. There will be two relays(dim and bright)at each headlight. I'm wondering if you couldn't do the same thing? Or do you have inside wiring issues and need to replace it too?
Working on dash panel issues with the B is impossible, as it barely comes away from the dash as the steering column is in the way and don't feel like unbolting it every time I work on it. Lucky the old truck has all original wiring with no real cuts/crimps/butt connectors floating around.