Or if you are truely serious about being a road racer, buy a set of coil overs and set it up as you wish. Again, you will not really need the measurement you are looking for.
Do you plan on using this as a track car? If not, just about any of the sets listed with lower the car, reduce body roll and improve you handling. Going any further is a waste of time because if you go much stiffer the car will be miserable on the road.
Current ride... '13 GTI Wolfsburg
BMW's from my past...
'92 535i/5 '89 325ix/5
'98 750iL '86 325(e)/5
'95 740iL '84 318i/5