KW v3 are OEM type (spring divorced from coilover)
However, because they use a PROGRESSIVE spring, you get a whacky, varied diameter spring in the rear like this:
For OEM type, coilover owners should get the SPL mid-link, which looks like THIS:
The SPL mid-link requires 65mm ID springs (roughly 2.5 inches)
This leads me to believe the progressive spring will NOT work with the SPL mid link.
My recommendation would be to CALL SPL and see what they recommend. They've always been super helpful.
or you can cancel the order on the stupid KW's and get fortunes or something that have more adjustment range and use linear springs