SSBC rear disc brakes with external parking brake

I am looking for help from anybody... I bought a 65 fastback with SSBC Force 10 brakes on all 4 corners. There is an external caliper on the rear brakes for the parking brake, but this was not connected. I have had no luck calling SSBC directly. It appears that these were an older style that are no longer being produced. Approx. 3 yrs ago. nobody has knowledge of how these were used is still working at SSBC. I bought their universal "L" brackets and still couldn't get enough travel in the cable to activate the brake. Can anybody offer any assistance? Thanks, Nick.