It was mentioned early on, but I'd go with a micro-switch. Easy to make a mounting bracket...a small piece of angle aluminum will do it. Set it so the brake lever closes it when the brake pedal is at rest and wire it so the normally open option is taken. Cut the mounting holes oval-shaped so you'll have easy adjustment. That way when the brake pedal is pushed, the switch's internal contacts will close and the brake lights will go on. The one in the image below was made in Switzerland, is about 1 inch wide and will handle up to 5 amps at 250 volts and I've seldom had one fail in the 60+ years I've used these. Good luck.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
