This forum has been helpful in a bunch of ways, so I wanted to post my build so others can get ideas too, and see what's possible.
I lived in my 4runner full time for 4 years with a very simple, practically "no build" configuration. I took a two year break, and will be moving back into it in a couple weeks, with an improved setup. Here it is:
255/80/17 tires which also fits in the spare location perfectly, and probably gives more clearance than the stock spare. It also has a 2" lift from toytec and body mount chop.
200 watts solar, tool case, 5 gallons extra water, trash case, weboost cell booster, and DIY awning for those hot summer days when I can't find a shady camp.
Solar wires run down the windshield into the engine bay. I'll probably have to replace the sticky zip-tie mounts periodically, but they're cheap and easily replaced. The sunroof was instrumental in doing the wiring for these. Without it I'm not sure how I could have done it.
100 amp hour group 27F AGM battery on a C4 fabrication battery tray. It doesn't fit the tray length-wise, but it does fit the space in the engine. I've got an extra bracket mounted on the end of the tray so that it won't slide around. You can't see the Redarc DC/DC charger which is behind the battery, on a bracket attached to the tray. Figuring out where to stick the Redarc was probably the hardest part of all of this. The blue thing on top is a bluetooth Victron 300 amp smart shunt battery monitor. The white thing ziptied to the battery is a wireless temperature sensor because I was curious about how hot it will get near the shunt. So far so good, but it's not the hottest part of the summer yet. Fingers crossed it doesn't melt the shunt.
ARB compressor, regularly used for 6 years and still going strong. Redundant circuit breaker for convenience to shut off all aux power running to the back of the truck. The lines are fused at the battery too. A horseshoe of LED string lights running around the engine bay to hopefully reduce the number of packrat visitors at 2 AM.
Fuse box in rear panel. Hardest part here is getting the 4 gauge wiring routed underneath the B pillar with the seatbelt. It takes some fiddling, but can be done with patience. You need 25 feet of cable to reach from the passenger side auxiliary battery to the rear. Not pictured, a Blue sea 12V socket and USB distribution panel mounted to the right.
Minimal sleeping platform. Just enough for a shallow drawer underneath. Room for two storage boxes underneath the refrigerator, only one of them is accessible from the inside. 30 quart refrigerator.
Extinguisher, small inverter for laptop charging, two LED dimmer switches, and Weboost mounted to panel.
Motorcycle cargo net up top for sleeping bag/coat/backpack and other light items. Clothing shelves, tilted and banded to keep stuff from falling out. I could get a lot more space by removing the driver side seat, but I use it for eating away from the flying insects, getting out of grimey shoes, etc. Dry food goes in the big drawer, fruit, potatoes, onions, go into the hammock on the left. The refrigerator is accessible from the inside as well as the outside. My kitchen items go into a tote that gets strapped to the top of the drawer. There's a pull-out table below the drawer that I can use as a shelf for doing whatever, or take all the way out and attach legs for use as a laptop desk.
I have room for food, kitchen, clothing, hiking and backpacking gear, 8 gallons of water inside in the front passenger footwell (plus 5 on the roof), and that's about it. It's a very minimal lifestyle, but I like it that way.