1969 Chevy El Camino Ball Joints Bad?

Best way to do this is to jack the car up under the lower control arm. Put a bar beetween the spindle and control arm and see if it wil move up and down. Do this on both sides. If it moves like a 1/4" then they need replacing. If they are original they will have rivets that need to be cut and punched out. Bu tyou should check your whole suspension system for play not only the joints.