I bought an OEM E12 arm and bushings from the dealer for 95 bucks and I had no issue swapping out the bushing. I learned this info from La Jolla BMW which has focused on these cars for years and has a great reputation. I would blame the parts and not the concept which is solid and has been carried out by others without a problem.
That's great and I'm glad it worked for you but something has changed and it does not work now. We even talked to the La Jolla folks and had the right part. We also talked to Ireland Engineering and it checked out again.
These were Moog control arms. Certainly a reputable company so maybe they are doing something different.
I'm just want members to know this is not a sure thing.