Originally Posted by Army

I'm doing similar work on my W123 - the FSM has loads of information on this (well actually the W126 manual). Unfortunately this involves lots of crawling around!

So stick with the blue print posted by MBeige for an easy life!

On the W123 / W126 you need to measure the distance between two points on the trailing arm - just under the hub next to the dust shield and the centre of the inner trailing arm mount. On the front you need to measure the distance between the centre of the LCA mount bolt and a point just under the shock absorber mount.

The FSM also says you can measure from the centre of the wheel to the fender on each wheel and that there shouldn't be more than a certain difference between each side.