Hey- thought I'd help out. '88 420SEL ride height:
Front Left- 3"
Front Right- 3 1/2"
Rear Left- 2"
Rear Right- 1 3/4"
These measurements are with a sagging rear end, before I got new springs in the rear only. The springs raised it about a 1/2" on each side I think, and improved the ride and handling significantly.
From what I've read, the rear subframe mounts tend to go bad on 126's, can anyone comment on this?