Pat, on the oil canning on the rear of the cab, that might be taken care of by the 3 stretcher bars that you haven't reinstalled yet. I'd get those in before addressing any oil can issues. If the rear of the cab is pretty much even (no visible dents) then I don't think you'll have a problem once the stretcher bars are in. If you still have some oil canning, deal with that then by doing a bit of shrinking.
Robert (MPandC) was kind enough to walk me through on a Facetime call the procedure to get rid of it on my roof. What you need to do is cycle the oil can and observe where the perimeter of it is, then apply pressure around the perimeter with one hand and attempt to cycle the oil can with the other using the same amount of pressure. The spot where you have pressure around the perimeter that stops the oil canning is where you need to shrink the metal. Robert may be willing to do the same for you if you send him a PM.
On the door gap at the bottom, if you haven't changed the door shape and your rockers are in the right place, I wouldn't worry too much about it. It's on the bottom of the doors and the seal at the floor level (top of the rockers) will help seal the bottoms, even if the weatherstrip on the bottom doesn't reach the rockers. If the fit of the doors is good on front, rear and top, I'd say you're good to go.
