Hubcentric vs spacers
The spacers are needed for the M3 wheels due to the larger offset of the wheel. Without the spacers the inside of the wheel/tire would rub on struts/shocks and possible other components. With the spacers, the wheel is pushed outwards and will have the clearance to be mounted. You will probably need longer mounting bolts or studs. These are different than hubcentric rings. The rings are used to fill the gap around the hub. ie- e39 hubs are ~74mm and e34 hubs are ~72mm, so the rings would be used to makeup this difference (fill the gap).
I've heard that the M3 wheels will rub the fender on tight turns on e34's, but they do look nice.
Good Luck-
Chip
'92 535i 5sp
EAT chip, Sachs kit, RRT sport control and upper thrust arms, SS brakelines, Camber plates, Subframe inserts, 3.64 Diff, M5 (3.6L) calipers.
'87 325iS