PART NO.  SPL.PAGE  DESCRIPTION                                                           
27H7394   15.H.4    Cylinder assembly -wheel (2) (rear drum brakes, 1500)
27H7394   16.H.4    Cylinder assembly -wheel (2) (rear drum brakes, 1600 and 1600-MK-II)

There is a tech article under Faulty Parts refering to the small sliding gap in the slave cylinder when it may not fit properly.

And another tech article on Rear Brake Plate Corrosion than can cause misfit of the slave cylinder.