I assembled the parts of front-facing spare tire well, and it's no problem getting the spare in & out of it with tongue jack in vertical position [a relief].
Sliced front door & removed 12" of same, like I did with body shell. Pop-riveted & tack-welded together to check fit.
Reassembled doors to check alignment... need to tweak front one a bit before welding seam, as there's little-to-no gap at top between it & rear door, but not too bad [another big relief].
Front half-door will be welded shut, with a simple smoked plexiglass window in place, maybe sliding up & down with screen on outside?... access via stock rear doors, from either side.
Assuming I put a 3" memory foam mattress on the floor, it looks to have approx 3'6" of height from top of mattress to underside of roof... 7'6" of interior length and a bit over 4' of width---3' or so width in foot well under galley.