The PD-4107 introduced a higher passenger platform to provide more luggage capacity and the distinctive style informally known as the buffalo bus because of the profile of the humped roof. This basic style was used on all remaining intercity buses built by General motors.
GM built 1,267 of the PD-4107 including, in 1967, the last buses purchased from GM by Greyhound.
Minor changes were introduced in 68 model PD-4108 buses manufactured in 1970 and 1971. The P8M-4108A of which 232 were produced, was a 1972 update of the PD-4108 with minor changes.
Information from the Bus World Encyclopedia of Buses - 1988