S4R has a single sided swinger doesn't it? Ride height rod will be different (I think, someone who has more S4R knowledge might be along in a minute)
For a double sided swinger, the Monster chassis and ST's use virtually identical components. If you cross check the parts lists from Ducati.com you'll find that, as an example, most of the part numbers for the rear swingarm assembly are absolutely identical and some differ in that the number is the same, but there may be an A at the end of the number for monsters and a B at the end of an otherwise identical number for the ST.
I'm pretty sure (without actually cross checking) that the ride height adjuster for the 1000DS Monster, the S4 and the whole ST range is identical
If not, then I have an ST2 ride height adjuster and we have an 03 M620S here which has the adustable ride height. I can go dig out the bits if you need me to, and the ST rod is spare.