Hi,
I have a 63 wagon, The car hasa fluid preasure sensor. When increased preasure is applied it grounds a wire that basically is your switch.
Look under the hood, driver side on the fire wall is your mayonaise jar master cylender. Comming out of it are your two brake lines. One of the line, probably right against the MC you wlll see the inline preasure sensor with the one electrical wire conneting. Its pulling the ground from the body of the car. Anyway. What I would do to test the switch is use a test light.
remove the wire from the switch and attach the clamp part of the test light, then run a lead from the needle of your test light over to your battery. Now have someone get in the car and push the brake peddle.. If the light iluminates then you got a bad wire that goes from the sensor to to the tail lights (which is cheapest but probably the most labor to fix). If it doesnt, then the switch is bad. (might try the test with the ignition switch (car key) in the on position).
It also maybe a bad connection at the switch, might take a tooth brush and make that connector on the switch shinny again.