GMC introduced the third and final generation of GMC C/K for the 1973 model year. The GMC C/K was an upmarket version of the Chevrolet C/K, and was offered in light, medium, and heavy duty variants. This new generation featured redesigned styling, leading to the third generation being commonly referred to as 'square body'. A wide range of V8 engines were available, as well as a few inline six, and one V6 option. As with previous C/K models, rear wheel drive variants were designated 'C,' while four wheel drive variants were designated 'K.' Starting in 1975, three trim levels were offered: Sierra, Sierra Grande, and High Sierra. At the end of C/K production in 1987, GMC continued their line of trucks under the GMC Sierra name.