The most you'd have to do is change you front strut mounts. Rears go right in.
With the exception of e34s with sls suspension systems which deal with airride and such.
e34 Struts and springs are all interchangeable within the model line, e32, and e24 (e24 fronts yes, e24 rears ???).
Not sure if we can use e28 and e31 struts. But all four model lines also can swap brake calipers. Which in some cases are good cheap upgrades.
Brembo or porsche 4 pot front calipers anyone?!?