Springs support your car and provide the "cushion" for the ride. The shocks control the cushioning motion. They slow the bounce down to prevent it acting like a po-go stick. If they (shocks) are worn, there is no control of the springs action, and curves or bumps in the road will allow the car to wallow, or sway. If your shocks have some miles or age on them, I would replace them first. If the car doesn't sit at the right height or have enough support after you remove the extended shackles, I would buy new springs.