You can buy brand new Z06 springs from SDPC2000.com for $60. Why buy used when new is about the same price? Under .550" lift is tame. If you put 1.5 ratio rockers on a cam designed for 1.7s you are going to lose lift. You probably should check with Lunati to verify you use your stock 1.7s or 1.5s. 1.5s are usually stock ratio for the OBS engines if I remember correctly.