Engine 651 in model 900, 906, 907 with code HK4 (Rear air conditioning, reinforced) Engine 651 in model 906, 907 with code N62 (PTO at front with bracket for extra alternator) Engine 651 in model 906, 907 with code N63 (PTO at front with bracket for extra refrigerant compressor) Engine 651 in model 906 with code H08 (Roof-mounted air conditioning system, reinforced)ws1300n3007b