2007 Chevrolet Silverado 3500 Classic Engine: 6.0L V8; Bore: 51 mm | w/RPO Code JH6 (9900 Lb. GVW; Power Brakes; Hydraulically Boosted; 4 Wheel Disc); Position: Rear;. 2007 Chevrolet Silverado 3500 Classic Engine: 8.1L V8; Bore: 51 mm | w/RPO Code JH6 (9900 Lb. ).