My '75 had the 14 bolt as original, and the parking brake setup is simple.
There is a large main cable installed in a U shape on the earlier trucks.
- open ends of the U are connected to the rear brakes, with guide brackets in the back that keep the cable parallel to the frame, and a metal connector bracket to attach the main cable to each of the parking brake cables.
- at the front of the U the driver's side is pulled out and to the left by the cable from the parking brake, and it can be adjusted there
- the right side of the U is held in shape with a bent metal rod that loops around the cable and then hooks into the frame on that side, holding the cable forward and to the right.
I bought a new main cable and then found some heavy (maybe 3/8"?) rod that I could bend into the right shape to hook onto the frame and hold the cable in place.
Bruce