CHEVROLET SILVERADO 1500 2003 with RPO Code JC3(Vacuum Power, 4 Wheel Disc, 6400lb); with Single Piston Rear Calipers; 6 Lugs. CHEVROLET SILVERADO 1500 2004 with RPO Code JH1 (Hydraulic Power, 4 Wheel Disc, 6400lb); with RPO Code JC3 (Vacuum Power, 4 Wheel Disc, 6400lb); with Single Piston Rear Calipers; 6 Lugs.