That dropbox wiring diagram file is nice & clear when you blow it up. Excellent ! Thanks Keith.
I have drawn for you, just the stop light/brake circuit. It couldn't be simpler, as it is powered all the time, & doesn't pass through the ignition, or other switches.
See how simple it looks, when you separate it from all the other circuits.
Get yourself a automotive tester probe (< $ 10 at SCA) and connect the alligator clip to the chassis somewhere. Then start at the positive battery terminal & the bulb will light, (assuming the battery -ve to chassis connection is fine)
Then move along the circuit, in a clockwise direction, at each side of the fusible link; either side of the 15A fuse; and the "powered" side of the footbrake switch. If you have "light" up to there, check the other side of the switch, with the brake pedal down. If still OK, then get someone to hold the brake pedal down, or bridge or s/c the switch out, and move along to the two LH & RH bulbs in the boot. If still OK, but still no break lights, then either both bulbs are blown, or the chassis connection of the rear light clusters is o/c.
With that approach, you must find/discover the problem.
You never know, in doing so, you may be lucky, and also solve the other gauge light issues, if it's a common earthing/chassis connection or the like.
If that solves your brake lights, then approach the other guage light & turn indicators in the same manner, after drawing out their individual circuits.
If you need any more help, just give us a yell.
I'm quite aware, how hard it is to follow those auto wiring diagrams, but it really is quite simple, once you break it down to an individual circuit.
Cheers Banjo