the after market shocks come with that spacer. the original shock mount bolts were a double ended stud, one end goes thru the rear mount and gets a nut, then this leaves a spacer (which is all part of the same double ended stud) and then a stud facing back for the shock to go ovet then another nut. you can still buy these thru year one and other sources. but if you are going to use those, yes you need the spacer. it allows you to tighten down on the shock mount with out pulling the shock itself against the rear mount.