Well its a total pain. You have to have a baseline, so you have to mount the body back down and just go from there. HUGE TIP-- get some really good quality duct tape-- I used the black Gorilla tape-- and put it over the hole in the frame just below the mounts right behind the seats. I put the WH 1" bodylift/body mount kit on mine and lost the spacers into the bowels of the frame never to be fished out again.. LOL!! All kidding aside, a hole saw and some welding the hole in the side of the frame up again the spacer was retrieved. HUGE PITA. I replaced the floors in mine and part of the door hinge panel, so some shimming was needed. Mainly for me in the rear most part of the bed. I just worked one side then the next and a buddy really helps a lot. Another tip-- you can change the size of the holes on the actual door hinge and where the hinge bolts to the body-- but dont change the holes in the door as it causes the hinge to physically hit the door instantly chipping paint. Going to the metal yard and having them shear some various thicknesses of aluminum-- from pretty thin to about 1/8"- to the height of the hinge makes it very easy to make shims that go behind the hinge against the hinge pillar. Most important tip is just be slow and methodical with no time frame. If you get it bam on the first shot- buy a lotto ticket

-- if not keep a level head and when you get pissed off-- go inside, watch 30 minutes of TV and relax. I guess one more thing- if you haven't painted the parts first that would make things much easier but if you have, then spend the $7 a roll on the wide 3M yellow tape-- as it will save your butt on the chips-- and dont remove it until you are completely done. Ive got some chip touchup due to not following this rule.