I could have got that answer from any BMW main agent. Of course if I could source the exact same part at a reasonable price I would not have asked the question. I wanted an informed answer as to why it would not or could be made to work. It would have helped even if you could have told me the differences in the 2 parts. This "stock" answer is of no use at all. If it had been the engine being changed over rather than the gearbox I know the answer. They would work..... all be it with some additional bits being changed. So do you want to have another go? Or are you unable to source the information that I have asked for?
This information does not exist. BMW does not keep a database of what parts can be crossed with what other parts - they are not in the business of building pieced together cars from multiple different sources. The only way to know would be to try and see, or find somebody, a single individual, who has tried this EXACT swap. The rule that any professional goes by is part number matching. No professional would try or advise trying to install a non-matching part number.
I know about engines not automatic gearbox's. I know that repair kits for both these gearbox's come back with the same part numbers. I also know that these GM units go in to many makes of cars. So can you explain to me what the "alpha" code numbers actually mean along with the calibration code numbers? That may well help me.