A regular cab that can seat two or three across is standard for the Sierra 3500HD. For more passenger capacity, double and crew cabs are offered, which can seat up to six occupants. The long bed ...

The regular-cab model seats three with 44.5 inches of legroom and 43.1 inches of headroom. Double-cab models can seat up to six, with the same front dimensions plus 35.2 inches of rear legroom and ...