You cannot, for the most part see the wear on these. However you can jack the vehicle up and support the lower a-arm with a jack stand and get under the vehicle and move the tire left to right and watch for ever so slight movement in them. It can be hard to decipher. A buddy may help by moving the tire for you to aid in visibility.
When I originally got my rig I replaced the upper control arm shafts within the first year of ownership upon recommendation of an alignment shop. 10 years later I looked under my vehicle, which I do more than anyone I know, and was amazed to see the lower control shaft wearing through the bushing. I replaced those with lower ball joints 3 years ago and now need to do the same side upper that the bottom was worn thru. I just about ordered a complete component set from Jegs, all MOOG. All USA parts, no mixed up junk from a local retailer. I have owned the truck for over 13 years now.
I am very happy about my purchase and finally getting my front end together to get my truck from acting like a drunkard going down the road.
See this:
http://67-72chevytrucks.com/vboard/s...d.php?t=770382