RE: Shock spacers
The spacers are a cheaper alternative to threaded shock bodies, but the effect is the same. They allow you to alter the ride height of your car by compressing (or uncompressing) the springs. Some people think that adding spacers makes the shock stiffer, but this isn't really true. Shock stiffness is determined more by shock oil and piston choice. A lot of people setup their cars, using collars or threaded bodies, so the lower suspension arms are level.