Well, this forum is not very active anymore, so you're probably going to be doing most of the work yourself! I've been planning a 3UZ conversion for my 2013 Hiace van for a few years, but I'm still not yet at the wrenching stage. However, I have slowly been accumulating information and planning my conversion to the point where I have a clear game plan and I think I have now addressed most of the potential issues which may arise.
1. Has the particular swap been done before? If so, a lot of the doubt about "will it fit" will be eliminated. But, there will still be many, many things to worry about. Integration of the 3UZ and its wiring with the vehicle's existing wiring is especially challenging. You will probably need to keep both systems more or less intact, so the new ECM runs the engine/trans and the original ECM runs the rest of the vehicle. Instrumentation can be an issue (though Yuri at All4Swap has an interface box that allows you to use an LS430 panel with a 3UZ), as can getting the vehicle's Air Conditioning, Air Bag and ABS systems to function properly post-swap.
2. Depending on where you live, it is pretty easy to get an engine with the OEM harness and ECM. But you need to specify that the ECM and (uncut) loom are included in the price, or they might not be. Or you can buy a donor vehicle and pull the engine and whatever else you need out of it. I like that idea, because you're able to experience the components in their "natural environment", so you know they work. But, it is more expensive than buying the parts, and you will end up with a useless shell on your driveway which you will have to get rid of somehow.
3. You will need to find the correct Workshop Manual and Electrical Wiring Diagrams for your new 3UZ. There are essentially two different ones, depending on whether the engine originally had a 5-speed or a 6-speed automatic gearbox.
4. Watch Kelvin's videos on everything UZ (
https://www.youtube.com/c/CartuneNZ), and Chris' videos on the engine wiring harness (
https://www.youtube.com/c/PhoenixEngineManagement).
5. They say the last 10% of a conversion takes 90% of the time. Good luck!
Ciao,
JZH
