Transmission identification help
 

I am buying a 1956 210 sedan and its all apart (was put in a barn in 1986). The engine that comes with it is a 350, has had a 12 bolt rear put in it, the trany has me boggled. I am sure I don't have the right set of numbers wrote down but this is what is stamped on the side....

GM 7
8858988
8285
Can anyone help me with these please?

Your numbers do not make any sense. Are you sure you copied them correctly?

I may not have, I have tried to do research on them myself and have come up empty handed. It is a manual, and looks very simular to a muncie 21. I'll pull it out in the sunlight and look again, post a picture even. thanks so far.