The upper rear of the cab is bolted to the lower rear, but then the interior panels are spot welded on, covering the bolt heads. There are also some welds at the door lock pillar. It would be do-able if the inner panels are removed. The joints at the lower portion of the windshield are lapped and spot welded, then lead finished. Melt the lead out of those joints on both cabs, and use a spot weld cutter, which should get the alignment fairly close. Measure the windshield opening height prior to cutting and make that match when welding things back together.
