I somehow missed this thread when it was new seven years ago (!), but I want to protest the listed rates for the OMP springs. I've been running them on my DD for a few years now, and they aren't really that much stiffer than SPG springs. I'll have to check the measurements sometime when I'm under the car.

My buddy put them on his spring dyno and measured the fronts at 460#

After doing some more research and seeing other posts on here I decided I will order some 400 or 450 lb springs for the rear. The numbers in Geoff's chart are all calculated I believe.