An old thread at this point, but here's my take on the subject and current setup:
2014 370Z Nismo, factory shocks at this point. Lot's of Track Days and a Daily Driver. why not, it's a drivers car after all. Lots of aftermarket stuff but this thread is about suspension.
Rear:
SPL Rear Camber, Traction and Mid-Links. Swift 6" 65mm, 12kg springs (with nylon and steel thrust washers on the springs).
Front:
Still Factory, but not for long.
My initial impression is 6" Swift springs are the right length. Whether you chose 10kg, 12kg, or 20kg, they are a snap to swap and only additional drive time will tell on the stiffer or softer rating. 7 inch springs are too long. I would only want to adjust the ride height lower a bit, otherwise the adjustment cups might catch on stuff the more you let them poke out the bottom of the mid-link arm. With the instructions included, I adjusted the cup at or near the upper limit. This gives me exactly a factory ride height using a swift 6" spring.
Shout out to the
SPLParts.com folks and for the helpful people there. They gave me great advice and aided in the spring selection and I look forward to doing more business with them.
Hope this helps some of you on the fence about what to get. If you haven't done so, reach out to SPL and ask them detailed questions. I did, no regrets.