Parts? Are 3.4L gasoline V-6's common around the world? I have no idea, but I always assumed the ability to run Diesel, and not very good diesel at that, was one of the things that is focused on for expo rigs. You can get an 80 series with a diesel.
I completely disagree that the 4runner is an "suited rig". The new ones maybe, but the 3rd gens are small inside. You can haul plenty of gear for a week out in the woods, but not a multi month expedition. It is a small interior.
IMO cargo space is at a premium for expo rigs, and the land cruiser is much larger in side than the 4 runner. (The amount of stuff that I struggle to smush in the back of my 4runner fits in an 80 with ease).
With the 80, you can also get factory lockers, whereas in the 4 runner, you can only get a factory locker. An ARB, or detroit is an easy fix, but it is one more thing you have to outfit the truck with.
Are you sure you've seen so many tons of Tacoma's on actual expeditions? Sure, I've seen a few, more than 4runners, but that is because of the above stated reasons. The Tacoma is simply a better platform than the 4runner, all things being equal. Its just easier to fit more gear in a larger vehicle. Mostly I see Tacoma's outfitted for overlanding, which you claim is not the purpose of your question.
But, and again, I don't know, I only have my own experience here, I've seen far more 70 series, 40 series, UVT's, Mercs, etc... on long, multi-national expos, than I've seen Tacoma's or 80s. Heck, tons of motor cycles too.
Hilux Surfs (same vehicle, different name) are most commonly found with a diesel or the V6 (there are some slight differences in parts between markets for emissions and such, but that's the same with 80s).
Land Cruisers could be had triple locked, '99/'00 4Runners had available rear lockers and the transfer case is mechanically locked AND selectable. You're essentially only down one factory locker (which is easily rectified for what it's worth, though I don't know that I intend to do so for all the use it gets).
The LC head gasket issues, PHH, and knuckles are potential liabilities compared to the 4Runner's CV axles.
You may be right about overlanding versus expo with the Tacos. That would make far more sense. There are definitely more 70-series, Defenders, etc. out there than just 80 series, but I'm only really concerned with/considering what's available here (US) now.
Using MSN Autos as a reference, '00 4Runner Vs. '97 Land Cruiser (both the last vintages with the appropriate equipment available from the factory)
.................................4Runner.................Land Cruiser..............Delta.........Advantage
Seating.......................5 (+2 optional*)......5 (+2 optional)...........0.............Draw
Front Headroom...........39.3"......................40.3"........................1"............LC
Rear Headroom............38.7".....................39.7"........................1".............LC
Front Legroom.............42.6"......................42.2"........................0.4...........4R
Rear Legroom..............34.9".....................33.6"........................1.3"...........4R
Cargo Length...............45"†.......................46.7"........................1.7"..........LC
Width @ Wheelwell.......38.3".....................44.1".........................5.8"..........LC
Width @ Wall...............41.7".....................58.1".........................16.4"........LC
Depth.........................38.7".....................42.2".........................3.5"..........LC
Curb Weight (manual)...3440#....................4751#.......................1311#.......4R
Length........................183.3"...................189.8"........................6.5"..........4R
Width..........................66.5".....................76.0"........................9.5"..........4R
Ground Clearance.........9.8".......................10.8".........................1"............LC
HP.............................183hp.....................212hp.......................29hp.........LC
Towing Capacity...........5,000#...................5,000#......................0#...........Draw
Payload......................1365#....................1719#........................354#........LC
Fuel Capacity...............18.5 gal..................25.1 gal.....................6.6 gal......LC
Fuel Economy..............17/20.....................13/15.........................4/5..........4R
Projected Hwy Range•...370.0.....................376.5.........................6.5..........LC
*MSN Auto did not have data, filled in by author.
†Ditto, save it's hard to tell where they're measuring from; I went from base of upright back seat to edge of what would be considered interior trim.
•Not a provided stat, but important for our purposes
There may be other useful criteria, but those were the specs that looked most important to me. I'm not arguing that the 4Runner is somehow a better vehicle than the Land Cruiser, just that it's very close where it counts and different in other ways that may give it a slight advantage depending on one's priorities. The fact that it's so close combined with the lack of them out there is confusing to me. Hence the thread.
It has nothing to do with what I'm personally doing or not doing, I'm not meaning any of this as any sort of self-conscious defense of my choice of vehicle, it was just an observation made (a lack of 4Runners compared to 80-series) that didn't seem to line up with the specs of the vehicles. Depending on one's priorities, either could be the better choice. My personal priorities (manual transmission, fuel economy, reliability, etc.) put the 4Runner over the 80. It surprises me that it's not a more common choice.