I never got around to installing these on my car, but the previous owner daily drove them. The spring rates are 350 lb/in for the front and 250 lb/in for the rear. The Ground Control website says that they will work on a P5, not sure about the differences in shocks though: http://www.ground-control-store.com/products/description.php/II=47
I saw them listed on evasive for $350 uric and they listed that they only work with stock, boge, or Sachs struts...makes.me wonder since I've read that some.people have used tokico. I'm still interested, pm coming your way
I've been toying with picking a set up, but I have to pay a monster invoice for manifold castings. If these are still available in a few weeks I'll take them. Otherwise GLWS!