Begin by setting the car to the stance you want to achieve. If you’re lowering the car, you’ll likely have to remove the springs and shocks to do this. Use floor jacks to raise or lower the body to achieve the desired visual relationship between wheel opening and tire, then measure the distance between the upper and lower shock mount attaching points for both the front and rear suspension. I parked my car on blocks of wood that gave just enough room for me to slide under. It’s good to have a helper when you do this.