Rear disc help on a 71 Mach 1?!?

We have a 71 Mustang Mach 1 at work with a 351C, 4 speed, and a 9" rear. The customer bought it on ebay being told it was in "perfect condition" but of course that wasn't the case. Anyway, the car has rear disc brakes on it with what looks like FRONT Cadillac calipers. Yes, that's right. There is no e-brake. I believe that we can put REAR calipers on the rear, but what cables do we need to attach the Cadillac calipers to the factory e-brake pedal? The customer would rather not buy an expensive rear disc kit when everything else works fine this way. Thanks for your help!
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