call tirerack... about $40 for 4 aluminium ones...
... think the part # is like t790 or something... and think it's like 72.4 to 74.. but if you tell them it's to put E39 wheels on an E34 they'll be able to figure it out for you.... the metal ones will rest into the wheel, then put the wheel on the hub... if you put the ring on the hub and press it flush, it'll miss the wheel and the hub is deeper than the portion of the wheel that sits on the hub... (thus put the ring onto the wheel, then carefully put the wheel onto the hub... -Rob.