If it is like a Chevrolet, which I think it is, it is mounted underneath the floorboards with a arm that rests under the brake pedal linkage. When you step on the brake the arm drops and turns on the brake lights.
I have been around more Chevrolet's and that is the way they are from the 40's or before until 1959.
If I am wrong, I am sure someone will come along and correct me.
Good luck with your project.
Jim
