sentences:  In 1979, the 6-71 was replaced by the 6V92, making all available Detroit Diesel engines V-engines; the 6V71 was discontinued after 1980.Following the launch of the cabover product line in 1969, the GMC Astro quickly exceeded the Chevrolet Titan in sales and market share.In 1981, General Motors ended sales of heavy trucks by the Chevrolet Division, leading to the cancellation of the Chevrolet Bruin, Bison, and Titan.