I'm getting ready to do this same job as well on my '86 300E. The rubber bushings are shot in at least one pair of arms, so I've been gathering parts to replace all the suspension arms, the subframe and differential mounts etc. When replacing the link arms, I believe that when you tighten all the nuts and bolts you have to make sure that the rear suspension is sitting at the same level as when it's on the ground under it's own weight. Otherwise, the rubber components will be stressed all the time and wear out very prematurely. I imagine that there must be a particular requirement, like the driveshafts must be level, or something like that, but I just don't know offhand what it is. Maybe someone else can chime in and enlighten us.