5610, 5900 Series Tractor (9/1990 to 12/1993). 256 CID 4 Cyl Diesel; Also Fits 555C and 555D. 4.4 Inch Bore, 4.2 Inch Stroke, Mexican Hat Bowl, Rect. Top, 1.5 Inch Pin, Late Rod. BOK Engine kit numbers consist of: Pistons, Piston Pins, Rings, Rod Bearings, Main Bearings, Full Gasket Set, and Seals. VOK Valve Train kit numbers consist of: Intake and Exhaust Valves, Valve Springs, and Valve Keepers.