Well, I found them. E189517 is what I had been basing most of my search off of. Here's what I've worked out. In that picture, the Upfitter Switch plug as shown in Purple, was barried under the 3 heavy (0 AWG?) wires, and all of the bundles going forward to the vehicle, engine, inverter, etc.
1) The upfitter switch wires do end up in a square, four pin connector (pg 119 C33-H). I varified this by hooking a voltmeter up, to one pin at a time and cycling the upfitter switches on and off. Confirmed, ~12VDC in accordance with the switch. 1=Yellow, 2=Green/Brown, 3=Purple/Blue, 4-Brown. I'll go back and edit this post later tonight with a picture.
2) In E189517, you see two other plugs, in the forward part of the battery compartment that are not highlighted (grayed out). The forward most one is C33-E, Vehicle Interface Connector, E189516. This is empty on my way (seems almost like a OBDII test, interface, sensor plug) and relatively easily accessed from the front of the driver's seat with the battery cover off.
3) The other plug, unable to find it in the BEMM, is for the inverter. I traced the wires, and it goes out of the side of the box into the bottom of the parking brake handle cover for the inverter. The inverter is located under the plastic cover at the base of the parking brake handle. All of the snaps are easy to get off and the only scary thing is pulling the cover off of the outlet face (if you look inside once the back of the cover is lifted, you'll see that some low profile snaps slide up the sides of the outlet cover. It sounds like you're breaking plastic, but it's more of a friction holder than an firm snap.).
4) The AUX fuse panel, not shown in the owner's manual at all, is where the 4 20A fuses are located for the upfitter switches. E189518. I had this open and confirmed the fuses were there; haven't done any experimenting yet. Just happy to find the switch outputs and have access.
5) One of the highlights of my day is learning about Customer Connection Points on the driver's left seat base (192338). Holy cow; this is cool. The cap comes off easily and gives you 3, threaded, 60A fused, posts to supply heavier loads than the upfitter switches.
I'll shift from my mobile brain dump (still sitting in the driveway in the dark posting) and ask for some advice from those more experienced that me.
Q: I'm thinking of hooking my House Bank up to the 60A post for charging and putting a simply relay into one of the upfitter switch spots. The van is ON, I flip the switch to close the relay and I get power. The van is OFF, or I flip the switch off to conserve the Van batteries, and I don't have power to the House Bank/Charger.
For those interested: I do have what I would consider a lot done on my conversion. This is my first time building a van, and I have a full time job, so I've been burning a lot of midnight oil.
1) ~4" hard foam in the window voids, single layer of Reflectix behind the Polypro panels from the factory.
2) Full wrap of the ceiling and upper walls in Reflectix, with some selective spots of Roadkill Sound deadening mat (Dynamat) and 1.5" hard foam. I sprayed foam into the ribs and odd spaces.
3) 2x205A 6V Apex deep cycle batteries (in the process of wiring) behind the driver's seat.
4) 60" oak cabinets with a 48" homemade hard wood counter top and a 48" overhead cabinet.
5) Full size futon mattress with a memory foam mattress topper in an integrated bad platform (mates into the cabinet and it all self-supporting.
6) 50gal polyeth water tank going to a spigot in the counter top and a kitchen sink spray faucet that goes out the door for showers.
7. 48"x60" with a 30" extension drawer that slides the entire rear floor of the van out of the back doors. The 90" part is for our tandem bike. This will make more sense when I post pictures.
8) I've also seen a lot of questions about winter tires. OK Tire Factory got me a set of Nokian WR C Cargo (Hakkapalitta?) tires for $1000 installed...they're highly reviews elsewhere, have the proper load rating, and make the wife and I feel more comfortable. I wasn't happy with the other tire options and the pushback from tire dealers. Hard to find proper tire sizes online as well.
Sorry for the long post; I finally had a moment of euphoria when I find those stupid wires. I wanted to share the success and give an update on the build. I probably broke a bunch of forum etiquette but, hey, I'm excited. Hope to post more soon.