The Bilstien Sports will work well with shorter springs. Stock springs and comforts can be used to make a great handling 124 car. Been there, done that.

Ages ago I put a set of Sportline sway bars on my 300E. I ran them for a long time and wore out a set of KYB shocks and struts in that time period (KYB big mistake.)

When it came time to do it over, I put Bilstien comforts all around and put the stock front sway bar back on along with a 500E sway bar in the rear. The reason is that stiffening the rear sway bar TAKES AWAY understeer while stiffening the front bar ADDS understeer. SOOoooo..... to take away as much understeer as possible (of which almost all factory cars have plenty of) leave the front sway bar stock and stiffen the daylights out of the rear one.

The Sportline sway bars work on a sportline car because they also use sportline springs. With stock springs, my setup is far superior. It does add a little more front body lean which to the uneducated is objectionable. You should not concentrate on minimizing body lean. You should concentrate on making the car go where you steer it. My final recipe did that. It took out LOTS of the understeer and made it a REALLY fun car to drive. Try it!

BTW, the aftermarket sway bar companies want to sell you TWO sway bars, not just one. They claim that their combination is two bars that are designed to work together. I say BUNK! They are selling stuff and they want to sell as much as possible. Stiffen the back sway bar before changing anything else except the shocks and struts. Try it, you'll like it!