When replacing the four 13mm bolts, the FSM reccomends purchasing new bolts with the pre-applied threadlocked...reccomendation here is clean and re apply blue loctite.

I purchased a Febi mount and the bolt holes did not line right up - I put my old mount back on at the conclusion of my rear axle job.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car