W126 500SEL rear end clunk

[quaid]

I have a clunking from the right rear end of my '85 500 SEL without SLS.
In normal day to day driving, it doesn't occur... Only when I go over speed bumps at anything other than a crawl.

If I bounce that corner of the car by hand, I can get it to make the noise.

I crawled underneath and the spring doesn't look broken.

I thought the rear sway bar links... so I ordered some but they came as rods about 6" long with a ball joint on either end... I need some that are just like a bush in a bracket that bolts straight onto the sway bar.

Is there anything else that its likely to be before I pull the car to pieces at the weekend? I can think of the muffler knocking, the shock top mount, sway bar mount... anything else?