On 65-70 fullsize GM cars, a large bolt holds the lower control arm onto the frame. The bolt incorporates a keyed eccentric cam that rides in a slot on the frame and allows camber and caster adjustment. Mark the orientation of the eccentric cam to maintain the camber setting when you reinstall the arms. Remove the nut on the back of the eccentric bolt, pull off the eccentric cam, and drive the bolt out with a punch. Remove the lower control arm.