1970 C20 Manual Transmision Identification Help.

[DEESTER157]

Hey all, I just purchased a 1970 C20. The previous owner was in the process of converting it to an automatic. It is a factory manual truck. I got the original transmision with the truck but I was trying to determine if this is the original transmision or even the correct one as I am trying to go back with the original manual transmission. It is a 4 speed and the only number I have gotten off of it so far is on the passenger side of the case. This number is C 96041W. Haven’t been able to determine what this is. Are there more codes or numbers in other places? Any help with this would be greatly appreciated. Thanks