How to you rate and specify shocks and struts other than the part number and application used for? Do they have any spring rate or dampening rate, like springs do? What is the difference between the FE1, FE2, FE3, and FE4? Im getting KYB FE1 replacements with the Eibach springs, and I’am trying to get specification for the springs and the shocks with struts. Any information will help…