First, my intention is not to offend in any way.
I see a pretty complete vehicle but the body is terrible and the frame isn't much better. I think of rust (from "best" to "worst") as light surface rust (easily removed with a Scotchbrite pad), some minor pitting, heavy pitting, some perforation and extensive perforation. The frame is well beyond "surface rust". Rust is pervasive and it makes the job much less fun. Many, if not most, bolts break off when you try and remove them. When you start cutting away rusty panels you end up cutting (and replacing) much more than you originally thought would be necessary. Costs escalate rapidly! To replace a panel there has to be something to attach (weld) it to. If the adjoining panel has rust issues when you try to weld to it, it will disappear.
As I said above I don't want to offend you, but my personal opinion is this is not a good candidate, and like brooklyn and Yellow Jacket said, get another FJ40 without the rust issues and combine the two. The one listed on in the LA craigslist may or may not have cut wheel wells and it's possible the diamond plate may be for looks and not just hiding rust. I don't know, but it would be worth your time to ask for a bunch of photos and perhaps a local 'Mudder could check it out for you. I did note that while that is listed as a 1978 the windshield frame is from an earlier vehicle. The best sheet metal is oem.
I didn't see a top, side doors or ambulance doors in your photos and I don't recall that you mentioned those. What's your plan with a top and doors?
Good luck with your project!