WTB-full size Gmc parts

just buy 2" lowering shackles and it should level it out. your spring width is 2.5" and i think the shackles were the same on chevys from 73-06. i just always run stock shocks with 2" shackles as its not much drop… if your an ext cab you might need shims

http://store.summitracing.com/egnsearch.asp?N=700+4294925130+4294839061+4294842007+4294908216+115+4294907438