I ordered a B12 kit in mid November for this year's track season. Suspension is sufficiently complicated that I like to bet on sure things rather than try to piece things together. It is very easy to make a great suspension good, and quite difficult to make a great suspension excellent.

After waiting several months for the boat to never arrive, I found someone at Bilstein USA who was willing to spill the beans.

The shocks are the same part numbers (24-110068 front and 24-110075 rear) as the B8 / Sport shocks. The compression and rebound rates listed in the specs are also the same (181/145 and 142/115).

The part number for the Eibach spring set is E-90-55-007-01-22. From what I can tell in reading foreign language web sites, these have the same rates and lengths as the Eibach Pro-Kit set (5544.140). The rates are linear 188 front and progressive 97-148 rear. A tech rep from Eibach is supposed to call me back in a few minutes to tell me if he could get confirmation from the engineers that they are in fact the same springs. If so, it appears you can build your own B12 kit instead of ordering it from Germany. I will update the post as soon as I know.

[UPDATE]

Eibach did in fact confirm they are the same springs.

 

A word of caution on this kit. According to a conversation I had with a Bilstein tech rep, the B12 kit lowers the Series 2 car twice as much as the listed amount, which comes to about 2.5" front and 2.125" rear.