Transmisson Gear Set Interchange

[corsair_kid1979]

So I have started the teardown of the 78-casting, three-speed transmission I acquired and found that at some point in its past it had an earlier ('32-35) gear set installed in it. What gear sets from these later years will interchange with the 78-casting case? I have order the Vanpelt book and waiting on it in the mail, but would like to start putting the feelers out to source another transmission.

I heard the '39-48 ones will work, but is that only for cars or truck transmissions.