It's the big bushing with the ears. If you didn't loosen the huge nut, it could be put back on car as is. No need marking anything.
If you did loosen the huge nut, put everything back on car loosely torqued. Load up the suspension, paint a line straight across the bushing to the arm. Take everything off and torque the big nut 180ftlb with the paint mark lined up. You can reassemble the rest pretty straight forward, and load up the suspension again to get the big bushing ears to line up to the chassis.