175 lb. rate QA1 AlumaMatic adjustable coil over on the Checkered Racing 4-link kit is now recommended. As for the length of travel compressed and extended , ask the manufacturer of your 4 link what they recommend. They have it all pre-engineered. If you're building it from scratch, call and talk to QA1 tech department, they can probably give you good advice. Too many variables to provide a part number .