On the E30 (3-series) the front suspension base is part of the sub-frame. On the contemporary E34 (5-series), not so.
A large steel rod links the bottom of the front hub to the mounting point on the sub-frame.
If you are planning to remove the front suspension base or hub, or the sub-frame, you’ll probably have to remove the 19 mm nut and bolt that attaches the rod to the sub-frame. At the hub side, the rod has some flex, so I could use a small hammer to tap the rod away from sub-frame, after the 19 mm nut and bolt were removed.
The rearward-facing fastener is in close proximity to a welded steel structure that made it non-viable for me to get a socket into position there, so the socket went in front, and I used an open-ended wrench at the rear.
If the nut comes loose easily, life is good, but in one case out of six so far, it didn’t, and it was so tight that I couldn’t loosen it even with all of my upper body strength. Penetrating oil, and tapping the fastener with a hammer, was the next step. So far, even that hasn’t done the trick, so I’m investing in a long breaker bar, next.