I replaced the lower controls arms for the very reason your pictures show. The lead bushing on both sides had separated from the control arm. Stupid design; - should have been a spool bushing just like the rear one. How many cars has GM built with lower control arms with two spool bushings do you think? - how about millions.
The OEM sway bar is actually a piece of tempered pipe that has been pressed on both ends and a hole punched through for the links.
The torque or twist from one side lifting while the other pushes down is so severe side for side, that eventually the pipe breaks in exactly the places yours and mine did.
I took my sway bar out, cleaned up the pieces with a wire brush attached to my grinder and then clamped the sway bar ends in a vise. Using my MIG welder, I re-welded the two halves together on each end, then went all around the inside and outside of the ends with a bead to finish it off. After a little grinding and polishing, and a coat of rust paint, I reassembled it and the noise went away. That was 4 years ago...still going strong.
The clunk can also occur due to the angle of the shocks in the upper shock mount. As the wheel is turned on its axis, the camber angle changes. To allow for this, the mount has a certain amount of give in it. But, unfortunately, the give also allows the bores on the shocks to wear and eventually the shaft inside the shock will actually shift as the wheels are turned left to right.
You can sometimes see (and feel) this clunk happen while the vehicle is stationary. While someone turns the wheels left to right watch the shock mount from inside the engine bay (after dark with a flashlight).
Also, the clunk can be felt if you hold the coil spring or the shock as the wheel is being turned. What you are seeing and feeling is the shock re-centering itself under the centerline of its axis as the camber angle shifts from straight ahead to right or left.