1982 Chevrolet Truck brake light problem

okay my 82 k20 brake lights will not work the wiring was cut before i bought it because it had a brake booster box installed but was not finished there are 2 green wires and a black wire that has power to it if you wire the 2 green wires together they dont work if you wire the black to a green the tail lights come on like the head light switch is on (there is the same outcome which ever green wire is tied to the black) im not sure were to go from here i also cant seem to find a good wiring diagram