2 questions here, if anyone can provide help it is much appreciated:

1. What is the best way to install a toggle switch to control whether my TH350C trans will lock or not. I would like to have the option of not locking with the switch open, but retain the original function with switch closed. I am thinking maybe wire the switch in series with the TC brake switch, that way with it open-no lockup, then switch closed-back to normal. Should be easy to splice into the wires there too and put my toggle switch below the dash. Has anyone done something similar? This is for my '84 non-ECM C-10 pickup, btw.

2. Also, I am pretty sure my trans has 4 wires going into the connector on the driver's side, what are they? I know one must be +12V, maybe one ground, but what about the other 2?

Many thanks for anyone who can offer some advice!