My next overland rig??? HELP!

[Holland]

Find yourself a 100 series and build out the inferior. You can easily pull out all the seats and put in a sleeping platform, and Outback Proven is importing aux tanks to give you added fuel range.

This is my vote.

 

[Kaisen]

The issue with most of your suggestions falls into one of two catergories, not enough power for highway speeds under expedition loads or too poor fuel mileage to go really long distance.
Suburban: A little big for most trails and poor mileage. Will not fit in a 20' container with proper bumpers and winch. Great value for the money and would make a great Americas overland rig.
Still not sure. Looking at a Japanese '88 Landcruiser with high top an 12HT diesel. Think it might just fit the bill. Thoughts or other ideas?

1988 Land Cruiser HJ61:
Length w/ factory winch 4995mm (196.7" long)
Width w/o mirrors 1885mm (74.1" wide)
Height w/ safari "hi-top" roof and stock 31.5" tires 2180mm (85.8" tall)
Weight w/ winch and safari roof 2200kg (4580 lbs)
12HT Tubodiesel Power 134hp and 232 lb-ft torque
Stock 4.11 gears with stock 31.5" tires, stock 0.845 5th gear = 100kph (62mph) @ 2200 rpm for a 15.5L/100Km fuel rate (~15.5 mpg)
Stock fuel tank 90L (23.8 gals) for a 580 km range (360 miles)
Length of cargo floor to front seatbacks/console 1830mm (72.0") -- That's 6'0", Not 6'3"
...
Hey, it will fit in a container and it's probably small enough for trails.....
...
1991 Suburban V20 (3/4 ton 4x4):
Length 219.1" -- interior of 20ft ISO container is 231.1"
Width 79.6" (5.5" wider -- not enough to matter on the trail?)
Height 76.1" (several inches lower than a HJ61 Safari)
Weight 4540 pounds (about the same weight as a HJ61 w/ winch!!!!)
5.7L V8 (Gasoline Injected) Power 200 horsepower 310 lb-ft torque (60 more horsepower and 60 more lb-ft torque, and similar curb weight ---hmmmm)
Stock 3.73 gears with stock 31.7" tires, stock 0.75 4th gear = 100kph (62mph) @ 1800 rpm for a 15.0L/100Km fuel rate (~16 mpg)
Stock fuel tank 151.4L (40.0 gals) for a 1000 km range (620 miles)
Length of cargo floor to front seatbacks/console -- well over 8ft (and more than 4 ft wide between wheel wells)
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Just sayin'
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And the world's nicest 1991 Suburban V20 would be way less than half the price of a similar 1988 HJ61 Safari
I think for some it's more emotional than rational. You'll buy what you like, and justify it

 

[4D55 Performance]

Instead of trying to reinvent the wheel I recommend finding a build that you like and then modifying it to fit your needs.

I know you have mentioned the Gen III Montero. The 2003+ models have the larger 3.8 engine and which is efficient and provides adequate power. I would not be too concerned that it is a unibody construction. They are very well built vehicles and they are every bit as tough as a body on frame construction vehicle. The biggest concern with the Gen III Montero is not the vehicle itself but it is the limited aftermarket. Aftermarket parts are available but you selection is limited to just a couple of choices.