UPDATE: I went to sears and bought a 6" 1/2" drive extension. I already own a large 1/2" drive breaker bar....then went to track down a 1/2" drive 8mm hex bit socket (found it at a local parts store). When I got the tools together, I used the set-up to break loose the 8mm hex head bolts on the motor mounts (1984 300D). This 1/2" breaker bar 8mm hex bit socket drive set up worked GREAT to break loose the main 8mm motor mount bolts!

Didn't finish tightening the 6mm hex head bolts until late last evening, I had diesel grease all over my face, arms and hands. This repair has been a lot of work! Tonight I am lowering the engine down on the new Lemforder mounts and reinstalling the 8mm hex head bolts; hopefully the engine will line up so the bolts will be easy to install.