The RPO J56 caliper as used on 205 of the 602 Z-28s built in '67 was a single pin design and externally looked no different than any other 4-piston disc brake caliper used on a '67 production line Camaro. When you removed the disc brake pads, then you could observe the heat insulators on the brake pistons. With that being said, there was an over-the-counter service part available that was a heavier duty verison of this caliper. It had the same heat insulators but the boss for the single pin was machined off and the opening for the disc brake pads was enlarged to accept the twin-pin metallic brake pads used for Corvette racing applications (also denoted as J56). The inner and outer casting halves of the Camaro caliper were drilled to accept the two cotter pins which located these Corvette pads in the Camaro caliper. Extremely rare pieces.
As noted in the '68 Z/28 brochure and a few other places, these are for the 11" rotors (J52 disc/drum), not the 4-wheel disc brake 11.75" rotors.
P/N 5468886 Caliper Assy, Front Disc Brake L.H. (special design)
P/N 5468887 Caliper Assy, Front Disc Brake R.H. (special design)
P/N 5468882 Pads, Caliper (for above) (special material)