The balljoint isn't replaceable on any 400E.

By welding it on, it's thinner and provides more clearance for the bigger brakes. Factory control arms are $330 and aftermarket febi are $197.

I think based on age/mileage I'd just replace the brgs. Chk idler arm bushing for play and the steering dampener.

For install brg races, I use to simply on a bench grinder reduce the OD on the old race(removed with a punch). Use it a board and a hammer to gentle get it started, and make sure it goes in straight and seats. Pack the brgs- think MB says 65 g per side(?). A tube is 150 g. Pack both brgs, a finger full on the inside and outside brgs + a dap in the cap.

M