You need to find out if all of the engine "updates" were done. Including,dual row timing chain,gears,tensioner,steel inserts in the block for headbolts.
These engines had single row timing chains until (83 I think) when mercedes probably got tired of all the cars showing up with bent valves due to the "lightweight" chains jumping time. They also had alot of head leakage problems because the bolt threads in the block would pull with thermal expansion. The fix for this was to pull the heads and install steel inserts in the block using a special template. It always surprised me that mercedes didn't seem to know better, becuase porsche had a similar problem with case bolt threads stripping for many years.