I have a Muncie four speed that a freind gave me, and I'm trying to identify it. The casting # on the case is 3925660. According to the Muncie transmision website this number translates to a 1969 M-20. There is also what appears to be a V.I.N. on the side of the case where the tail shaft bolts to the main case. That number is 19WS43323P9K024. Using the V.I.N decoder on 1963chevy.com this nuber translates to a 1963 corvette . Am I missing something?