Here's what I've been told. The 4 leaf springs give you the stock ride height from the beginning, but then when they settle (a few years / 1000's miles) they tend to make the rear end too low. The 5 leafs, sit a bit higher initially, but when they settle they sit about stock height. Validity? I don't know, but I believe I put 5 leafs on mine, and it looks stock. I can check this weekend when I get the car back from the shop. I buy my springs from ESPO in PA. They have been great, and always ensure a proper spring. You can find them on the web.