The update program commenced in late 2002 with production launch slated to be fall of 2004. The engineering team chose the engine variant out of the GMT560 truck (the C4500) because it packaged better into the H1 engine bay; however, 23 engine component changes were required and the team had to do a 2. 0 in (51 mm) body lift to accommodate the taller engine and its turbo housing (a prior 0. 5 in (13 mm) lift had been done for MY96 to accommodate the turbo on the 6. 5L engine). The 8th digit of the VIN is 3, setting this version of the 6. 6L Duramax apart from the versions used in pickup trucks. The GMT560 engine calibration was used with minimal modification; engine output was 300 hp (220 kW) and 520 lb⋅ft (705 N⋅m) of torque. The Duramax engine was equipped with cooled exhaust gas recirculation and an internal engine oil cooler, thus, requiring a 40 percent heat rejection increase to engine coolant. Because space was limited between the air-lift brackets that protrude from the hood, the fan system was modified by putting it directly under the coolpack and driving it through a special gearbox directly off the crankshaft damper pulley. Several other cooling system modifications were required to assist with cold starting from −30 °F (−34 °C).