Purchased a 2000 Excursion 4wd with the 7.3 even though I knew it was from the north. Sure enough, rust....and a lot of it. I banged away with large flat head all around that I could get to and just flakes coming off, can’t punch through. Should I proceed with POR15 3 step, have cab off rehab, or place on autotrader? Ext and int are quite nice and motor in great shape. 158k Miles.