Just finished updating myself on the build. I have a 91 F350 factory 4x4 ambo modded by Wheeled Coach. I am not as close to finishing as yours, but thought I would comment on a couple of issues that we have in common. Maybe be of interest to you or someone else following along.
H1 rims:
I am running the 37" military MTR's. Truck was once a dually but now singles in the rear--I have a wide box so they look a little funny tucked in the rear. Spacers scare me on the rear (Sterling) as the box is heavy and aluminum and weight do not mix. I fear I will wind up like the broke ambo in Baja. Just finished recentering a set of 5 each 12 bolt H1 rims to 3.5" backspace--still need to pick them up from the powder coater and install my new to me load range E BFG Baja tires.
H1 rims come in several versions: 8 bolt, 12 bolt, new version 12 bolt (sometimes called 13 bolt), and the 24 bolt--bolt referring to the number of beadlock bolts. All beadlock H1 rims require an "insert" to keep the beads pressed against the rim. Factory backspacing is in the neighborhood of 7". 8 bolts are for the old 36" Bias tires and came with a two piece magnesium runflat insert. 12/24 bolts are for the radial tires - 36" Goodyear MT, 37" Goodyear MTR, and 37" BFG Baja. MTR's and BAJA can be load range D or E. The 12/24 rims have a heavy rubber one piece runflat insert instead of the magnesium insert. There are some aftermarket options--PVC pipe, Staun internal beadlocks. Many rockcrawlers cut down the magnesium runflats--in our case with top heavy ambo's, the runflat is nice if you get a flat or blowout--instead of dropping to the rim, it drops to the runflat. Might keep you from ending up on your side. Replacment tires are farily easy to find--you can even buy a pallet from GovLiquidations if you want!
rear box AC:
When I bought my ambo, the rear AC did not work. It came from Antarctica, and although religiously maintained, I guess they were not too worried about rear AC. the AC unit was enclosed and located by my head to the front of the box as entering the side door. Replacement parts were crazy expensive and hard to find. Further research indicated the rear AC unit relied on the stock 1991 F350 compressor to cool the cab as well as the box, connected by the longest set of AC lines you have ever seen (like 11 feet or so)? Found a pinhole in that long line, and after pricing a replacment since it could not be repaired, coupled with the fact the stock compressor could barely keep the cab cool, as well as Wanting the ability to run the AC wihtout the noisy IDI running the compressor under the hood, I ripped out the rear AC system. Bought the smallest window unit I could find at Walmart (great return policy!) since the truck is already tall and did not want more heigth with a top AC unit. Did some window AC unit research (those hydroponic growers have these things figured out!) Found a marine rated pop top exhaust fan to get rid of the heat--pop the top and it vents. Rains and I can close the vent. Only required me cutting a whole in the roof about the size of a coffee can to pop in the vent. Vent is about 2 inches tall when collapsed, and 4 inches tall when extended. Plenty of room to add solar on the roof later. Kept the factory vent (to the right of the side door) for air intake. Welded a bung to the case to route the condensation out the bottom of the truck. The install looks pretty good, and I only had to add a small hinged door next to window unit to access the fan vent (hooked the power to old AC unit power switch). I have not had a chance to try it yet in the real world, but looking forward to it.
The best thing about this forum is seeing and sharing with other guys so that we don't have to keep recreating the wheel..... Keep up the good work!