in desperate need of correct length lugs for Monoblock IIs on my 95 S00.
Just went thru the same thing, thinking I had to buy new lugs. Called a shop that specializes in lug bolts, and the guy was very helpful.
Take a lug bolt you are now using, or one laying around and put it thru a wheel hole on one of your Mon II wheels and hold it in place.
Now measure (in mm's) how much is sticking out the back side of the wheel.
I was told the ideal measurement is 17 to 20mm's.
Just do some simple math to calculate what size Bolt you need to fit right. Example, if your measurement is only 15, then measure the shank length, lets say the shank length is 34mm's. Since your short a few mm's you can order 39 mm shank bolts, which would put you at 20mm sticking out the back.
I was fortunate, as I tried my lug bolt on 3 different types of monoblocks, and they all measured in at about 20mm's. (my bolts are 39mm shank, and fit all my monoblock wheels perfectly)
So I was able to reuse all my lugbolts...
here is the place I called, they have all size lengths if you need new ones, call them if your not sure...