I'm not an expert on this so I can only relay what I've been told as it relates to the 124 wagon. I have one of these with hydropnematic on the rear and regular shocks on the front.

Both front and rear shocks are Boge, I think Boge and Sachs are now owned by the same company. Anyway the shock for the front of my wagon is supposedly tuned to work well with the rears. The front shock is a Boge Automatic. I'm happy with the vehicles handling.

I installed Bilstein heavy duty shocks on anyother 124, a sedan. They give the car a firmer feel.

With the hydropnematic shocks in the rear I'll be inclined to use front shocks that are compatible with the rears.

If I had the option of using heavy duty Bilsteins on my wagon both front and rear, I'd go that route.