Hi Erik,
so there are two versions of clutch bell housings and their corresponding slave cylinders.
View attachment 206332
View attachment 206330
The early version attached outside the bell housing, the upper one.
The later version attached to the bell housing by screws.
If you want to install the "Sportgetriebe" Getrag 265/5 you may use both versions.
If you want to install the "Schonganggetriebe" 265/6 only the later version will fit.
Both slave cylinders are still available, at 270€ and 50€ e.g. at W&N