Muncie 4 Speed

I am trying to put together a Muncie 4-Speed that came with my '67 Camaro. My problem is that it came disassembled and I have never messed with one of these trannys before. I know that mine is a 1963 only model. What I don't know is what makes it a '63 only. It looks to be pretty complete but I am using new bearings, rollers and synchros. In my researching I think I have a 1966-1970 main drive gear assembly. I was wondering if anyone knew if a later main drive gear assembly would fit it.

The Tranny Is A 63 Only Model?
Was The Tranny Out Of The Car When You Bought It?