I don't think the M1 shaft will be close enough, considering the M1 is based on a different platform the other 1 series. It would have to be modded, and chances are you will have to mod where the bearing carrier is. Keeping your original shaft would not entail moving the center bearing, just modding the rear part to fit the M3 or 5/7 series shaft.
Below, you can see the part numbers for the 135 and M3 driveshafts. You can also see their lengths.
135i Man = 1371mm, Auto = 1373mm
M3 Man = 1441mm, DCT = 1456mm
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