Detailed item info Model OverviewThe 2007 GMC Sierra Classic 2500HD and 3500HD heavy-duty pickups are available in a wide range of configurations to suit various work purposes. Three different engines are offered. with a 6. 0L V8 (making 300 horsepower and 360 lb-ft of torque) standard across the line. An 8. 1L V8 with 330 horsepower and 450 lb-ft is optional. as is a new version of GM's 6. 6L turbo-diesel V8 (making 360 horsepower and 650 lb-ft of torque). Depending on the model. the engines can be mated with a five-speed manual transmission. four-speed Hydra-Matic automatic. or six-speed Allison automatic. The five-speed manual is offered on all 2500HD models but optional only on some of the 3500 variants. The HD trucks are available in three bed lengths. three cab styles. and in 2WD or 4WD. The 2500HD models pair the crew cab with either the short or long bed. while the regular cab comes only with the long bed and the extended cab comes with either the standard or long bed. The 3500 models come only with the long bed. in regular cab. extended. or crew cab variants. The 2500 models can tow as much as 15. 00 pounds when properly equipped. while 3500 models can handle up to 16. 00 pounds. Sierra 3500 models come in SRW (single rear wheel) and DRW (double rear wheel) variants. the latter of which provide improved stability while towing heavy loads. Like the light-duty Sierra Classic. the HD Sierras vary rather dramatically inside as well. from the very basic Work Truck trim all the way up to the top SLE2 and SLT equipment levels. The SLT. for example. includes dual-zone automatic climate control. cruise control. leather power seats. steering wheel controls. an overhead console. and a Bose audio system with a six-disc CD changer. Options include more interior items such as power-adjustable pedals. and a reverse sensing system. but the long list mainly includes gear aimed at outfitting the HD for serious work duty. such as skid plates or a snow-plow prep package.