87 560SEL accumulator changed rear suspension still riding rough

[wawago]

Hi,
I have a 1987 560SEL. The rear suspension has been riding rough (clunk gunk when over bumps) and low for years. Recently I have changed the two accumulators. The ride has improved about 50% but some of the roughness and low rear suspension still persist. I am thinking about changing diff., subframe, and upper&lower strut mounts to eliminate the roughness. My question is how can i test whether the struts (shock absorbers) need to be changed too? Last to change spring shim do I need to compress the spring? Thanks very much

Rick