I recently took the plunge and bought a new-to-me used limited slip differential off of eBay. It came from an ’89 325is with 117k miles on it. It is nice and clean with little resistance while turning. It has 3.73 gears which are the same as what I was already running. This past week I decided I would put it in with a pair of new drive axles and brake lines. The new lines are also from eBay, I cannot remember the seller or brand but are braided steel wrapped around Teflon and look the part.