I read it else where the gearbox cross-member is different, so you will need to use your 1200 cross-member,the bolts used to attach the dustshield to the lower half of the bell housing are a different size, so get the 120Y dustshield and bolts if you can.The hole in the bell housing where the clutch cable goes through is larger on the 120Y gearbox.This can be rectified by using a 120Y clutch cable. An easier alternative is to make up a washer with an internal diameter equal to that of the hole in the 1200 gearbox, and use this when fitting the 1200 clutch cable onto the 120Y gearbox. Rather then that I have no more idea about it.