I have a 280SE 3.5 cab and can say that the springs are rarely the cause. But they have spacers above it and they have to be aligned perfectly. Also you have to look at the differential mount in the trunk. I just replaced all of this… The diff mount, trailing arm bushings, support mounts that run off the differential. Also the front stabilizer bar bushings, engine mounts, sub frame mounts, transmission mound, etc. etc. etc.The car definitely sits a little higher and more balanced. I have the compensating spring instead of the hydropneumatic compensator. They are a pain in the neck and they only last a couple years when they’re restored. Good luck I hope you find the issue