I wanted a small lift on my W350. I used front soft ride springs from Skyjacker. I believe they were called 1.5-2.5 because the height could vary depending on the application and weight. My truck had 5 leaves on the front originally and with the new springs gained about 2". The originals were under arched (like upside down) The new springs are almost strait across to slightly arched up. No other components on the front were added except new shocks.
For the rear I had standard rear springs with out overloads. Since I do pull trailers with it. I didn't want to change to a lighter/softer spring, And I didn't want the extra thick Add-a-leaf, But still needed 2 to 3" to level out the truck. This truck had 3" rear blocks originally, The Cummins trucks around 90-93 had a 6" block. So i picked up a set from the salvage and swapped them in for the 3" lift in the rear. I used rear shocks for a 92 W250.

The truck rides well for a 1 ton. The long wheel base helps too...(crew cab) I don't have any drive line vibrations. Really no reason too as its all OEM components other than the front spring.
Not sure if these rear blocks would work on your W100 But I know the front spring will. Sorry if this got a little long....