I removed the upper control arm with almost no effort on the driver’s side. The passenger side took a flame torch and an impact wrench. I sanded, primed and painted the upper spring seat prior to removing the upper control arm shaft, which yielded to a pipe wrench.

Putting in the new shaft proved to be quite challenging. With the taper end towards the rear of the car, and oil on the threads, it went in most of the way with just fingers. Then it got extremely tight. I eventually got it centered by slicing two of the old bushings into nuts. With one of the new bushings paired with a home-made nut on each end of the shaft, I was eventually able to work the shaft into the spring, using two wrenches and all my weight, until it was centered.

I need to add that real nuts with these (square) threads do not seem to exist; I checked all over with no avail.