I have a one piece bumper, added a 2" lift, and never lifted my steel bumper. I unfastened the bottom of the plastic bumper and never reattached them, the plastic will stretch over the steel still. Makes it so the stock skid still fastens in place. Easy peasy.I think you would need the bumper relocation bracket, regardless if you have a 1 piece or not. Behind the 1 piece plastic is a metal bumper that is fastened to the frame and sits right inside your 1 piece bumper cover, this would need to be moved up so your plastic 1 piece cover would still fit onto the bumper.