I have for sale spl rear midlinks for 370z/g37 along with the tein 2.5" springs your need to run the midlinks (cant use rear factor springs). The springs are 2.5" diameter and 7" length with 10kg spring rate exactly like SPL recommends. They are less then one week old. I am running coilovers and went back to the springs that came with the coils so those midlinks and springs need to go.
https://www.z1motorsports.com/suspen...37-p-6600.html
TEIN.com: RACING SPRING - PRODUCTS
These are over $1000 and they are practically brand new, selling for $700 firm including paypal fees and shipping.