The GM "old-look" bus was somewhat streamlined in appearance (resembling the PCC streetcar in styling), similar in shape to a loaf of sandwich bread, and had windows that were generally smaller than those found on more modern bus designs produced after the 1950s. Unlike most earlier buses, the GM "old-look" bus was built using a monocoque design, rather than a body-on-frame design, and it helped shepherd the change from gasoline to diesel-powered buses. Most "old-look" buses were powered with the Detroit Diesel 6-71 inline six-cylinder diesel engine, the exceptions being the shorter models that were powered by the four-cylinder version of the same diesel engine, and buses that were equipped with gasoline engines. Manual and automatic transmissions were available, with the Spicer angle-driv