The first aussie 116's had no self level, it wasn't till the k-jet models that it started in 1976, and the spring shims you mean on the top of the coils are in different thicknesses as to exactly level the car from factory, they aren't really critical but are of good use if yours are worn out.
A little trick i have done is to put 450slc amg springs in my 450sel and it lowers it perfectly and gives it a little nose down stance which makes it a lot better at higher speeds.
As for the shocks, i wouldn't really recommend you use monroe shocks, and from my experience the bilstein's are a lot better for the heavier cars.
You can readily get heavy duty spring from pedders, they are the same as w126 which pedders keep in stock, and the rear conversion from s/level is a much better option as it takes all the float out of the car and makes it solid on the road, without expsensive parts that could fail at any time.
My 1975 450SE race car had SLS from the factory, and its a D-jet car. I did however ditch the SLS, installed pedders rear springs (and lowered them, twice), lowered the front springs, and installed Monroe shocks on all 4 corners. As well as replacing the usual worn suspension bushes, idler arm bushes, ball joints etc. the car is now, as you say, very solid on the road, with none of the float we've become used to with our SLS W116s.