Exactly, the reason i did this was that the full coilover set from Vogtland is reasonable in pricerange, and you get everything you need. The sleeves is an addon, but only cost 45£ so thats manageble. Also i wanted the synergy of a full suspension set made for one particular car with similar weight destribution.
I have read loads of threads about people making their own coilover sets. One of them was on a E34 V8 where he used Toyota MR2 shocks. Now the MR2 is a midengined car so it really has no particular weight in the front (weight destribution is F43 R57 %, and to add even more the car is alot lighter total than a big fully fledged V8 powered E34. Maybe its just me, but it just don´t add up.
The E39 allthough almost twice the weight of a E21 has a weight destribution of F51.8 R48.2% where the E21 has a weight destribution of F51,7 R48,3%, -that is very similar and that is also one of the main reasons for me to go with the E39 setup. I don´t need to do alot of tests with different spring rates and shock absorbers, i can just get the whole set in one swift move.