I just ordered new ML-1925 4 leaf heavy duty springs from Eaton Detroit. I am upgrading from the 5 leaf Sprint springs to the 4 leaf 400 springs. I asked about the spring arch and Eaton said a replacement 5 leaf spring has an arch of 6.625". The HD 4 leaf spring has an arch of 5.25".

This is quite a difference from my spring. My car sits [censored] high IMO. My wheel arch is 27.25" up front and 29" in back. I'm hoping the HD spring will make the back sit a bit lower. I realize the shorter arch won't necessarily translate into lowering the car. The HD spring requires less arch than the SD spring. I will find out soon enough.