As dbischoff mentioned, changing the shim WILL change the ride height... NOT BY INCHES, but by exactly what the shim difference is...
The spring (and each spring in the world) is rated by LBs/In, that is a number that tells us a given spring will be an inch shorter, if you put x pounds on top of it. if the spring burls are equal in size and shape, then the spring is said to be linear; it will keep the same rate; put X pounds, and it gets shorter by 1 inch, put 2x on it, and it gets 2 inches shorter, and so on...
The merc springs are linear. since the body weight is not changing, the compressed height of the spring under the body weight DOES NOT CHANGE, let’s call it "H"... now if you wedge a shim "S" between the spring and the chassis, your overall compressed height of the spring will be "H+S"...
Difference in height for the most part in R129 that I’ve seen over the years is caused by using the wrong shock part number, because R129 used many confusing part numbers for shocks, and they were not changed based on model year, but rather, by VIN.
Many vendors are unaware of this fact, and sell shocks as one size fits all, and cause these issues with consumers...
When a shock of the wrong rating is used, specially when brand new, it could have enough internal gas pressure that bears weight, and makes really easy to lift the car up...
I know many are confused, thinking how can a shock lift a 2000 pound corner of a car? but remember, the shock is doing it with the help of the spring, thats already compressed, and pushing the body up...
to put in prospective, I am sure we all bragged to our friends when we were kids that we can lift our dad's car... if you remember, a ten years old can easily lift a car's body 1-2 inches up... because of the help of the spring... it is one thing to lift the body up an inch or two (suprisingly small number of Lbs force, 20-30lbs!) and its completely another to lift the wheel off the ground (2000 pounds)
So, yes! the wrong shock does have enough tention (gas pressure) to lift the car up an inch...