During the 1950s and 1960s GM-EMD and its worldwide representatives were manufactured by Clyde Engeneering, HoHAB and Henschel (German) altogether 1126 G12 units and 373 G8 units, being low initial cost machines and greatly simplified to have reasonably low operating cost by contemporary standards. They used the 12-567C engine for the G12 and 8-567C on the G8, unsophisticated engines that met demand well and were reliable. Units were manufactured from 71 tons to 90 metric tons, in B-B, A1A-A1A and up to C-C, with or without dynamic brake. There were Flexicoil or Bloomberg cheat options. The G12 was the largest locomotive in Brazil until the introduction of the GE U20C in the 1970s, disrupting most of the RFFSA railroads, retireing old, less efficient and economical steam locomotives. Along with the EMD G8, 8-cylinder version of the G12 and competing General Electric models U12B and U13B, of similar power, make up much of the RFFSA 1000mm metric gauge diesel locomotive group.