Did 2 tours in Okinawa. Owned some cool and interesting vehicles while there but didn't bring anything back. Okinawa is not the best place to pick up used cars due to rust. You are probably learning quickly now that you are there, but the longer you stay the more you will learn. As you probably have found out there a used car lots that cater to Americans and sell "Y plate cars" and those that cater to the Japanese selling only "Kanji plate cars" It is not that difficult to get a Kanji plate changed over to a Y plate.. Don't shy away from the lots that only cater to Japanese and don't have anyone that speak English. I did this once and the guy was totally cool and happy to work through the language barrier to make it happen.
....On the used engine sales. Japanese laws on car inspection "JCI" are made to encourage people to buy new cars to support the car manufacturers. Used cars become very expensive to get "JCI'd" every 2 years if you don't do your own work, and the Japanese do not work on their own cars as much as Americans do. Many Americans want to drive their vehicle till the day they leave and will junk it as opposed to selling it to someone. Landcruisers are more unique and probably not subject to this so much, but the on post recycle yards in Okinawa sold good running used engines from junked vehicles (that still ran and drove) for $400-600 each in 2013 to include diesel engines. That is 1/4 what you would pay for that in the US.
On engine swaps and matching numbers: The Japanese inspect everything when you get your vehicle JCI'd. They will inspect the engine number to see if it matches the title. When you modify your vehicle to non-original title specification to include making it 10mm wider with fender flares they may require you to get your title modified to reflect the change(your title lists the width and height of your vehicle). This requires a trip to the land transportation office for vehicle inspection, tax stamp purchase, and issuance of a new title....................The point of all that is to say that swaps and modifications are doable and done, but there are flaming hoops to jump through and it won't get past the Japanese without doing the proper steps...
Getting your older LC JCI'd while you are there.. Immediately before your inspection degrease, pressure wash and wipe clean all oil seepage, grease seepage, and leaks no matter how small. Put exhaust repair tape on any rusted exhaust fittings. Squirt black silicone RTV on a rag and wipe it across any cracked or torn rubber brake line, rubber hose, rubber grease boot, tires, or any other dry rotted cracked rubber part that is still in working condition. Old rubber brake lines are almost always dry rotted and have visible cracks in the surface, but not leaking. Even if not leaking they will fail you for the cracks. If your wiper blades are dry rotted they will fail you for inspection. The RTV trick should be done that night before inspection.
I know this is a landcruiser forum, but if you are a off roader and want something really cool, unique, and affordable do not overlook the mitsubishi J53 jeep. This is a licensed copy of the jeep CJ 3 produced by mitsubishi with both gas and diesel engines. They made them into the 90's and I'm not sure when they stopped. At one point they had the MMC 4D56 diesel the same as the Delica vans. Really nice ones with limited rust were $3.5-6K US in 2013 in Okinawa. This jeep is like a 1950's jeep but 40 years younger that has Japanese quality assembly and parts and gets 30MPG with a 4cyl turbodiesel............Compared to the LC though it is a jeep with no AC, smaller capacity, lightweight, and a soft top/soft door vehicle.
