I am not sure we are talking of the same strut/arm, but any of them require leveling the axle before tightening so the bubber bushing/insert you mention on each end is not under a twist load when the car is sitting normal. So leveling the axle before tighten assures this.[ the bushing does not float on the retaining bolts and is sandwiched, so if the axle is hanging off-level, the rubbers will be twisted when car is let back on ground.
I just did torsion arms on an E320 with the new part from
Parts Shop and did not notice a larger end. I am wondering if you have changed the Torque strut vs Torsion.
Here is the job from the cd.
Would this be the same arm/strut?