Quick update: found a used 15,000 BTU low profile roof AC unit with new gasket and interior control module. Found an awning that will fit the truck and a source on some inexpensive maxxfan DELUXE roof vents/fans. My stovetop works well now (yay!). Floooring in the back of the cab and insulation/soundproofing is in mostly. Ordered my dinette table parts.Have an appointment in 7 days to have my sofa/bed base built and my interior walls refinished à-la RV with prefinished panels as well as have a greywater tank installed. Pretty soon it will start feeling like an RV!
Comments regarding the passthrough: It improves the ergonomy of the truck better than I could have hoped for and the vinyl flooring in the front makes it feel like... an RV rather than the back of a firetruck. Also, found a jeep backseat that will, with minor mods, fit between my front seats. I have seatbelt mounting points built into the truck from the factory right behind where I want to position it so the kids will be able to ride in front with us when they want to OR in the back at the dinette.
Still LOTS of work to do but it's moving forward! It won't be the most polished build ever due to my time constraints but it will be comfortable and get my family out there (hopefully). Truck is still sort of for sale but.... it looks like I will finish building it in time for my trip!