Thanks for the info Zippy. I have the 456/7 springs on car now. The reason I want to replace is springs are sagging and my slicks rub sometimes. They are 18 years old never had a problem with them just starting to sag. I did run the cal trac set up one year they worked good but not enough to justify the extra money in my mind. So I sold that set up and put old SS springs back on. My track days are getting fewer every year.