you should not post questions in threads that contain links to other threads. I'll answer your question, and maybe the moderators can move your post to a thread of it's own.

You don't need an sls valve, you need new accumulators. The accumulators are what provides the damping for the suspension - think of a sphere with a dividing bladder inside - one side is the hydraulic fluid from the suspension, the other is compressed nitrogen gas. Eventually, the bladder ruptures and the gas mixes with the fluid and you have no damping. Since a fluid cannot be compressed, when you hit a bump, the only thing that compresses is the shock mounts and the tires - they're all hard rubber, and you get a bouncy ride.

I think they should be replaced in pairs. You can probably purchase them from the FastLane parts outlet here on the forum - in fact here's the link to the page where they're for sale:

http://catalog.peachparts.com/ShopByVehicle.epc?q=1995-Mb-E--3--0--Wagon-Suspension&yearid=1995%40%401995&makeid=MB%40%40MB%40%40X&modelid=E-320-004%40%40E+320+Wagon&catid=L%40%40Suspension&subcatid=L7040@@Accumulator&mode=PA

I think you need 2, one for each side, and they should be replaced in pairs. Others will confirm my suspicion.

This solution is far less costly than any conversion you might be considering, and retains the functionality for the car as MB had designed.