It was 41 to 47 production tranny.
it was out before 41. i have the same thing and i took the tail piece from a 46 and put it on my 40 to open the driveline.
There is an art to shifting those things from what I am told and most have not survived because people did no learn how to do it.
its not an art. its a procedure. people learned how to to do it and so will you. the reason they went away is because they came out with something better called the sm420.
if its bound up or not drain the oi, pull the stick out of it and pop the top and look inside. its a very simple transmission with straight cut sliding gears. depending where it was stored all it may need is a good flushing and new oil. until you open it up your just guessing
