im talking about the spring pirches that are welded to the axle tube the place that the springs bolt to on the axle and u may need to use wedges or other things like that to fix pinion angle if u use longer single shackles ur pinion angle and caster will be all out of wack, i sugjest using a boomerang shackle id check with white trash and get some more ideas befor starting be cause he knows more than me, with the longer shackels ur only raising the back half of the spring which is changing the pinion angle and caster an du would put a wedge in between the axle and the spring do u under stand now, sorry if im not a real good teacher, if that didnt make sence tell me and ill try to clarafy it i almost got lost reading it
