DavidM wrote:
I do not know how many 633/626 cars had front mounted and side mounted pumps or which came first however the side mounted pumps are attached to a lug cast into the cylinder block so retrofitting a side mounted pump to a block made for the front mounted pump involves some non factory modifications to support the pump. The side mounted pumps are of a similar design to other models in that they have an external easily adjusted gland nut.

In my limited experience the front mounted pumps are more common.