I just did my springs. There are heavy duty and regular springs. The two give the car the same ride height but the HD compresses less w/ weight.
The rubber pad goes on the top of the spring and can be identified by the number of nubs which can be seen w/ spring in place. All the cars I have seen came w/ the 2 nub pad but I have heard that MB used differing heights to balance sagging (L,R,F&R) cars. I have seen 20 year old pads in good condition but you won't be able to tell until they are removed. I put the 3 nub 19mm one in mine...should have just reused my stock 2 nub one but I already bought the 3 nubbers.
Autozone rents spring compressors for free...you want the inside the coil kind.

The old regular springs were the exact height as the new HD springs...no sag at all.

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82 300D....went to MB heaven
90 350 SDL....excercising con rods