Casing casting numbers mean nothing other than what tranny may have donated each part. I have heard many many guarantees that a Muncie is an M22. Never has the gaurantee made the trans an M22. Only the guts make it an M22. If you had the guts then you start looking at the casting numbers to see if they match the guts. That is, if the numbers really matter to you. To me, a Muncie for sale is either new/rebuilt or needs a rebuild.