Did you ever run the Rubicon?
I did. I've done it twice now. Couldn't go this year, but fingers crossed for next year again.
https://www.toyota-4runner.org/5th-gen-t4rs/259539-trip-report;-rubicon-2018-tlca-rubithon.html
My general thoughts are - it's rough but do-able. The lack of ground clearance will be an issue, so choose your lines carefully. And having someone who's got a lot of experience will help to choose the best lines goes a long way. As does having really good skid plates. Everything underneath will get pretty well abused.
What I would suggest as far as vehicle prep:
2.5-3" lift and as tall of tire as you can get in there. I had 33's the first time, 34's the second time. It did make a noticeable difference on taller tires.
Airbags in the rear. We go for about a week, so lots of gear = heavy and having the ability to max out the rear height with air springs for the worst parts was really useful. I normally otherwise have the rear set at around 2" of lift with light spring rates because my normal use is empty 99% of the time.
Full skid plate set including the fuel tank. It takes a beating, probably more than any other area. Skids for the shock mounts. I don't think the rear axle needs a skid plate other than maybe a welded on protection ring for the drain plug. You absolutely if nothing else need a skid for the transfer case and exhaust crossover. Wierdly - the stock muffler seems to be nearly immune from rocks. I've yet to do anything more than some light surface scratches. You also absolutely need rock sliders. And bumpout sliders are better for a few specific obstacles. I would also highly recommend wheel spacers - even though I kinda hate them. They put the tires out a bit more and keep the body off the rocks. I used them the second time, not the first and it really did help. But it also exposed the shock mounts worse.
If your skids don't cover them - find a way to protect the front cam tabs for the lower control arms. They'll get chewed up. Lots of options there. I don't think lower control arm skid plates have any meaningful use, but a small skid just for those or something like Marlin's kit would be even better.
The REAR lower control arms are very easy to bend and will get bent almost certainly if you dont either upgrade or reinforce them. If you are a welder or have access to one -they're very easy to reinforce with some light gauge steel channel. I did a writeup on that here:
Simple DIY Rear Lower Control Arm Upgrade
And IMO a winch is not entirely necessary to get through, but you shouldn't go without one. You'll use it. And it'll safe a lot of time stacking rocks and jacking. It'll help you keep moving at a reasonable pace. Second year I used the winch only one time I'm remembering right now. But it's really nice to know it's there.
The rear bumper will get hammered without protection. Front bumper will probably scrape a little bit here and there, but not bad. No need for high clearance side cuts.
I'd just go with one spare. First time I took 2 expecting more tire damage. My wheels got pretty well chewed up both times. Expect surface damage to the wheels. I don't think you can avoid that easily. The most common issue I saw was torn off valve stems. Bring a spare valve stem or two. Don't bring a second spare tire. The weight causes more harm than the extra tire does good.
I also took a spare CV axle - both sides are the same, so you can use one spare. I have never needed it. Actually - I've never had anything break. It's been pretty much bulletproof.
You should have more than enough fuel if you fill up in south Tahoe before going. I went through about half a tank of gas for the loop from South Tahoe to Loon lake - out Tahoma and back to South Tahoe.
Finally - having all the Trail stuff - rear locker, KDSS, and crawl were all useful. Crawl has been magic a few times that amazed me - and some people in my group. But those are maybe once per trip things. I think an SR5 with a winch would make it through with a little more effort in a few spots. ATRAC isn't quite as good as a rear locker and MTS - but it's perfectly functional.
Hope that helps if you're thinking about going. It's a lot of fun. It's an incredibly beautiful area. Do some hiking. There's so much to go see and explore off the trail.
Maybe next year I'll take my FJ40 - but probably not. The PITA of a trailer queen is that you have to drive about 2.5 hours on the road between the two ends once you're done. So you end up with an extra 5 hours or more of highway time at the end. And I store my FJ40 at my parent's in Montana - so that adds another 12 hours to go get it, and 12 hours back up to drop it back off. It just isn't practical for me to drive up to Montana, get it, then all the way down to California, then all the way back up to Montana and then turn around and go back again south to Utah where I live now. The 4Runner does perfectly fine for that trail, has a nice highway comfortable cruise out to California at 75mph and home. It's a swiss army knife and that's why I love it.
