the way this bolts on is it has the single groove stamped pulley bolted with three bolts to the balancer and then this sits inside the stamped pulley over top of the three bolts (it has notches to clear the heads of the bolts) and has three bolts go through it. the stamped pulley runs the alternator and the water pump i believe and this runs the power steering. (if i remember correctly) lol
also that picture makes the thing look HUGE but its actually the same diameter as the stamped pulley just sticks out about an inch or two farther