I'd do the spring lift, add the tires you want to use. Then measure for the shock length at the static height. Then, remove the 1 coil, and measure the most compression the tire will take before it hits the body. Measure for the shock length. You may have to redo the location of the bump stop. Remember this action is not an impact so adjust for 1/2" more compression for that on the bump stop measurement. (Meaning the compression impact will be greater compression than just lifting.) Find a shock to fit the length criteria. The closer you get to bottoming the shock without actually bottoming it, you'll get the most droop length. To add, remember the shock has to be a certain diameter otherwise it'll hit the axle housing during full droop. If you want to add a limiting strap, this will support the droop of the shock from fully drooping.