The Muncie or Saginaw 3-speed manual transmission serial number is located on the lower left side of the case adjacent to the rear of the cover. The 3-speed Tremec transmission has the number on the upper forward mounting flange.
The 4-speed transmission is numbered on the rear of the case, above the output shaft. The Turbo Hydra-Matic 350 serial number is on the right rear vertical surface on the fluid pan. The Turbo Hydra-Matic 400 is identified by a light blue plate attached to the right side, which is stamped with the serial number. The Powerglide transmission (through 1972 only) is stamped in the same location as the Turbo Hydra-Matic 350.