I recall reading somewhere that the A750f conversion from wholesale is in the ballpark of $12k usd for a diesel (1HZ, 1HD-T/FT), which is a simpler swap as the transmission bolts up without adapters.
So, be prepared for some sticker...
It's a fact, at least on the early models. FZJ cooler and hard lines bolt on.
The HDJ81 was only sold in Japan, maybe Toyota didn't consider it necessary for use there? I certainly consider it necessary for use in North America.
Trying to track down a loud whining noise I‘m getting on deceleration from higher speed (anything over ~70kph). Could be occurring during acceleration too but less noticeable if so. Almost sounds like loud straight cut gears, shifting trans...
If you have a mechanics stethoscope or can get your hands on one it might help you narrow down the engine noise. An extension held up to your ear can do it too. Try different areas on the engine and see if you can pinpoint it.