A 3/4 ton pickup based on the older General Motors full-sized truck frame, the 1999 GMC Sierra 2500 arrives in SL, SLE and SLT trim levels with rear-wheel and four-wheel drivetrains. With vinyl seating, four-wheel anti-lock brakes and AM/FM radio included on the SL trim, air conditioning as well as power windows are found on SLE versions of the 1999 Sierra 2500 truck. For some luxury in a work truck, the 1999 GMC Sierra 2500 pickup adds leather seating. All models of the 1999 GMC Sierra 2500 pickup is fitted with a 5.7 liter V-8 engine generating 255 horsepower funneled through a 5-speed manual gearbox. An optional four-speed automatic transmission choice can be mated with the engine. A 290 horsepower, 7.4 liter V-8 gasoline engine is optional on the 1999 GMC Sierra 2500 with a 6.5 liter turbodiesel V-8 powerplant also available. For a third fuel type option, 1999 Sierra 2500 pickup's can also be factory-converted to run compressed natural gas through the 5.7 liter V-8 powerplant.