Ford incorporated multiple upgrades to the F-250 HD model during its manufacturing phase starting in 1999 which added cooled gearbox technology as well as stronger rear axle design and reinforced suspension components to reach a 500-pound total weight increase above the base F-250 model. The Ford F-250 HD maintained the same strong performance characteristics enabled by the 1999 9th generation F-series chassis that previously operated the vehicle. Multiple wheelbase choices emerged during the release of Ford F-250 HD although building both the extended and double-long versions proved short-lived after their initial production phase. Customers choosing the 1999 Ford F-250 Super Duty could select between three powertrain options: the 5.4L Triton V8 generating 235 hp and the 6.8L Triton V10 producing 310 hp as well as the 7.3L Power Stroke diesel engine which generated 275 hp alongside 525 lb-ft of torque. When the F-250 HD 1999 debuted the engineers included the 6.4-liter Power Stroke diesel engine that provided 350 horsepower along with 650 lb-ft of torque. Engine components within F-250 HD received improvements that optimized transmission functions leading to better torque delivery and reduced fuel usage thus making the vehicle adaptive to weight-bearing and towing requirements. The new rear suspension system for the Ford F-250 HD improved handling with no compromise to performance specifications. Using factory-supplied Ford components maintains the F-250 HD's reliability and functionality for complex operational needs.