The uprights are modified E30 uprights - on the E30 the shock is mounted inside the upright which is a tube design - they chopped the top of the tube and weld in an insert with a thread for a metro ball joint, the factory mount design used the U bracket very similar to what I recreated:
https://www.realoem.com/bmw/enUS/sho...diagId=31_0143
On the E36 the shock is bolted from the back, I don't remember what the upright design looks like on the E36 version but I'll likey a bit different.
https://www.realoem.com/bmw/enUS/sho...diagId=31_1252