The GMC Sierra HD comes in many different configurations. The 2500 versions come in one of three body styles -- regular cab with a long bed, crew cab with a short bed and crew cab with a long bed. The 3500 body styles mirror those options but also offer the option of two extra wheels on the rear axles, useful for towing extra-heavy loads. Beyond that, both 2500 and 3500 are offered with either a 6.0L V8 making 360 horsepower or a 6.6L V8 turbodiesel making 445 horsepower and 910 pound-feet of torque. All 2500 and 3500 HD Sierras come with the option of having 4-wheel drive. Maximum tow ratings top out at 23,200 pounds on the 3500 when properly equipped. Trim levels for the 2500 and 3500 come in three different flavors. Work truck, SLE and SLT. SLT trims are only available on crew cab versions. In standard work truck trim, the vehicle is fairly basic with automatic door locks, air conditioning and cruise control, though HID projector-beam headlights are standard as well. SLE versions add OnStar, heated exterior mirrors, a leather-wrapped steering wheel, power windows and a CD/MP3 player. The SLT trim includes power seats, steering wheel mounted audio controls, a remote starter, dual-zone climate control, a Bose stereo, Bluetooth connectivity and power-folding mirrors. Denali versions come in only one trim level and in crew cab and short-bed. Regardless of bed-length, the Sierra HD Denali is packed with luxury goodies. Standard features on the Denali include perforated leather seating surfaces, heated and cooled 12-way power adjustable front seats, a premium sound system with a 9-month subscription to Sirius XM satellite radio, a heated, leather-wrapped steering wheel, auto-dimming rearview mirror with automatic garage door opener, power adjustable pedals and rear parking assist. The Denali also comes with a unique grill and other selected trim. Options across the Sierra HD range tend to be fairly utilitarian, with items such as a longer axle ratio, dual alternators and off-road suspension sprinkled across the checklist of options. However, more common items such as a rear seat entertainment system, a navigation system, wireless mobile device charging, a remote locking tailgate and a sunroof are also available on the Sierra HD.