I just plopped a Jap spec motor in my MKIV and would not recommend it. The throttle body and intake manifold are bit more different than you think. I am running into all sorts of problems and thinking about changing them both to US spec parts.
Make sure you get a Supra motor not just a JZA-80. There are many other cars that use this block, but have totally different oil pans, and many other parts! Don't be fooled or talked into any other setup.
Since I already was going to upgrade the cams and injectors, those weren't so much the issue. These engines are normally cheaper to acquire, but in the long run I am not finding any cost advantage since you'll need to buy parts for it. Yeah, not having the EGRs is nice, but $4 worth of steel to make block off plates can fix that in a minute.