Succeeding the Second Generation C/K series, the 3rd Gen Chevrolet C/K series was an all-new clean sheet redesign which debuted in mid-1972 for the 1973 model year. The redesign was revolutionary in appearance at the time, particularly the cab, departing from typical American pickup truck designs of the era. The 3rd Gen C/K is colloquially known as the "Square-Body" or "Box-Body" generation, although GM officially called these trucks "Rounded Line." The third-generation pickups were offered in multiple equipment level packages or trim packages, including the Scottsdale, Silverado, Sierra, and others. As seen on previous generations, Chevrolet designated rear wheel drive trucks with a C and all wheel drive trucks with a K. These letter designations were used alongside the numbers 10, 20, and 30, which denoted 1/2, 3/4, and 1 ton payload capacities. This system created six main variants, known as the C10, C20, C30, K10, K20, and K30. For 1987, Chevrolet changed their naming system, changing the C to an R, and the K to a V, in preparation for the launch of the Fourth Generation Chevrolet C/K. As is common with many popular vehicles, the 3rd Gen C/K was often converted into a Custom vehicle.