Some update: according to Alpina Buchloe, there is no such thing as Eibach springs for the early E24 B7 turbos. Alpina used the red references from the BMW catalog, i.e. the sport springs.
FYI, here are these:
front : ref 31331124004, 52,08 € piece, excl VAT
rear : ref 33531124007, 71,30 € piece, excl VAT .
These parts exist at BMW Germany, and have been ordered. It seems the problem is solved
PS both H1R and Eibach responded by Email they had no solution for me...