59 Upper Control Arm Bushings

I wanted to see if you guys only replace the screw-on bushings for upper control arms or if you actually replace the shaft. It appears that the bushings screw onto the shaft and the outer portion of the bushing threads into the control arm. So the part that moves are the threads on the shaft & bushings. Do you all find that the bushings bear the majority of the wear or do the threads on the shaft also take a beating?

Also, is the centering tool available anywhere to center the upper inner shaft (Tool T58P-3044-A)

Attachment 329