Muncie 4-speed - ChevelleStuff
Decoding Chevrolet VIN, trim tags, cowl tags, engine, engine block casting numbers, cylinder head . Muncie 4-speed Transmission (Group 4.000) - Casting Numbers . 3925660, 1968 - 1969, M20 2.52 1st, M21 2.20 1st, M22 2.20 1st .. The 1969 to 1974 Muncie got a ratio designating letter at the end of the date code.