Wiring Issue - Brake Lights (72 C10)

[devildriver6]

Okay, I could use some help here.
First off, let me start off by saying the wiring in this truck could use some tidying up.
That is to say....it's a mess.

So, here's the issue: all lights work, including turn signals, flashers, headlights, markers, etc.
The ONLY thing not working - brake lights. I swapped out the switch, no luck

Fuses are all good. Brake switch is new. Wiring all seems okay.
I'm not a wiring guy (yet...lol...this truck will turn me into one, I'm sure).

Any clues on where to start?