Hmmm.....
On mine I am running 500 front and 500 rear. The front is deliciously stiff, the rear is too bouncy. The rear is oversprung for the weight. A better setup would be 500 front, about 350-400 rear.
On the factory kw v3's that I still have on, spring rate was 400 front, rear was progressive at around 250-500ish range. The mismatch of linear and progressive springs, is the most annoying and unsettling shit you can do to a car. The front felt nice and well planted considering the weight of the car, the rear always felt untamed and all over the place.
I forget what the factory spring rates and exact corner weights were. I have to dig up those numbers from my ancient notes.
Anyway...
That's why I ask about spring rates. Now... with that kind of lift you have a ton of clearance and should have a fair amount more of suspension travel, so going softer will be desirable. Probably like a 250 front and 200 rear would be firm enough to reduce excessive squat/brake dive/sway to not feel dangerous, while still allowing that suspension to flex a little.
My numbers may be a little off. I'm quite high right now. But you get the idea.
Much love!