The MC-8 was the first model assembled at the new Transportation Manufacturing Corporation (TMC) plant established at Roswell, New Mexico in 1974. TMC became primarily the builder of buses for Greyhound Lines while the Motor Coach Industries plant at Pembina, North Dakota, which began MC-8 production in 1973, continued to assemble buses for other operators.
The original MC-8 had a slanted (parallelogram) window design with a wide blank panel midway which produced a seat pair on each side of the aisle with practically no window. These seats were always the last to fill up. Late in the production cycle, the window pattern was updated to eliminate the blind seats and provide larger windows to all. This same window pattern was continued in the next model, the MC-9.
Information from the Bus World Encyclopedia of Buses - 1988