Attempting to remove your roof at the factory spot welded areas will be difficult around the top windshield posts and door area. The back of the cab wouldn't be hard along the seam. If you can patch the dented/rusted area with a piece from the other roof that would be best. As for the drip rails, you could cut out a section of drip rail from your "spare" roof and patch it in. The other option would be to replace the roof entirely from the back seam section and at the front windshield posts. The posts would be easier at the front instead of the seam/lip area. You need to make sure you take careful measurements in this option as the fit of your windshield and doors will suffer/leak if not done right. I would try to take the least radical solution. ie. repair the damaged areas if possible and try not to remove the roof.

My cab was damaged in a roll over and we attemted to repair with another roof. Getting proper fit is critical. I ended up locating a replacement cab. Cost less than all estimates by any bodyshop.

Good luck.

Kevin