Chevrolet's heavy-duty work trucks under the Silverado banner out-gun and out-muscle others. The series also provides uncommonly comfortable passenger compartments in cabs with two or four doors, and they're smooth in suspension ride and downright easy to operate. These trucks in 2500HD and 3500HD series come with two-door Regular Cab, four-door Extended Cab, four-door Crew Cab and no-cab Chassis Cab. Exterior styling for 2003 conforms to the face-lift on Silverado LD trucks. Powerhouse engines and strong transmissions also apply, including two gasoline Vortec V8 choices plus a Duramax turbo-diesel V8. The Vortec 6000 300 hp 6.0-liter V8 is the entry plant. A Vortec 8100 8.1-liter big-block V8 is optional at 340 hp and works with either a ZF six-speed manual or Allison five-speed automatic. The Duramax 6600 6.6-liter V8 direct-injection turbo-diesel puts out king-of-the-road power and torque ratings, and it too mates with the ZF six-speed manual or Allison five-speed automatic. Silverado 1500 HD totes the 6.0-liter V8 and divides into two trims with LS and LT. The Regular Cab Silverado HD carries a bench seat for three and two front-hinged doors with a truck box in back of short or long length. Rear doors for the Extended Cab are hinged on rear edges and close by tucking behind front doors or open in the absence of pillars to provide a broad and unencumbered space for easy entry to both the front bench seat or rear three-person jump seat. For Crew Cab, with full-size rear area and full-size bench seat for three, the conventional front-hinged back doors work like front doors in an arrangement that emulates a sedan.