1967 Chevy C20 brake lights

[stahlberg]

Recently bought a truck and it has been torn apart and partly rewired. The tail lights work and the blinkers work, but the brake lights do not work. I think it is supposed to have a brake light switch, but there is no place on or near the brake pedal to mount it. I cannot exactly use the schematic diagram because there are so few connectors on this truck compared to what used to be there. Two wires go into the light sockets in the back and the socket itself is plastic. Was the original metal and was that used as a chassis ground? I have two wires running to the rear to use. One gives me 12 volts and the other is ground to chassis. Putting these on the light socket does nothing. What is the concept behind brake lights? Is there more voltage to the filament for brakes than there is for just tail lights?