For a tummy tuck you have to do a 1.25 inch body lift.
If you combine the 1.25 inch body lift with the 2.5 inch suspension lift, youll have too much room for 31’s. The 1.25 inch BL and 2.5 inch SL combination is ideal for 33’s.
Since you are wanting to stay on 31’s, a 1.25 inch body lift combined with a 1 inch H&R spring lift, would be perfect for a 31 inch tire and a tummy tuck.
Be aware you would need a SYE, a new driveshaft and adjustable links to alter the pinion angles.