I will put in my 8 cents worth. This sort of leading question, always brings 10 more, that I would ask. But first off, why did you buy a B trans with the idea of putting it into an A body. Are you not aware of the fit issues ahead of time? Without seeing the trans, I assume it was a good deal, and one that I would buy too, but know ahead that it is just a parts addition at this point. Save yourself a lot of trouble and acquire a correct A body transmission or at least a main shaft and extention housing to convert the B one. I might add this isnt that difficult a task, if you know your way around 833's.
note, I do have a large spline A extention housing.