Don is spot on. I had these calipers for years. Bought a rear disc conversion from SSBC and the only thing worse then the brakes was their customer service. The brake calipers were impossible to bleed. They would drag constantly no matter how much you tried to shim them. The emergency brake cable was constantly in a bind (which probably led to the brake drag) and even with the cable completely loose, they'd still drag.
I did finally find a fix, though...I took them off and threw them away (literally) b/c I refused to sell them to someone else and installed Baer Brakes all around. Never had a minute's trouble since.