All tranny's on BJ's are interchangeable, in that they will bolt up to the engine (I'm not sure if BJ-4X and BJ-60 trannys can be changed) and all BJ-60 tranny's are fully interchangeable (drive shaft lengths ARE different for the 5 speed and the 4 speed as are the floor plates) BUT FJ-XX and BJ-XX are NOT interchangeable unless the input shaft is changed. The 2F and the "B" series engines have a different requirement in that part. I don't know if it is bellhousing differences or what but it is known to be different.