On the 123 and 126 chassis the shock holds the spring in place by preventing the LCA from moving. To be safe it wouldn't be a bad idea to use something to prevent the spring from escaping "if" the shock or its fasteners failed for some reason. If you're going to replace the lower ball joint the vehicle can be positioned so that the chassis is supported off the ground and a jack or stand can support the LCA when the spindle is removed to replace the ball joint.