The E31's have EDC don't they? Meaning that the rear is self leveling and has electronically adjustable shocks. Very nice setup when all is good. But replacing EDC shocks is horrendously expensive.
If your E31 does have EDC and you do need a new set of shocks go read a bit about them & the rebuild service Sportsline offers for EDC shocks over here
http://www.m5board.com/vbulletin/e34...tions-faq.html
Just need to scroll down to the EDC III suspension part of the FAQ and there you'll find links to the threads about EDC & EDC rebuilds.
Need to rebuild/replace the two front EDC's on my E34. Might have to get a second job to pay for it if I want to do it anytime soon...