sentences:  From 1966 to 1970, GMC would use a separate conventional school bus chassis from Chevrolet, basing it on the H6500 instead of the medium-duty Chevrolet C60 (in 1971, GMC would return to a medium-duty chassis).In the mid-1970s, General Motors began shifting away from its alphanumeric nomenclature for truck names.While still using the H/J name internally, the redesign brought new names to the vehicles.