At the time when I was installing the engine, it was not very mature especially wiring etc as I think there were only 1 or 2 swaps done in Peshawar and at that time not in any 4x4s.
Honestly the swap was not that difficult, all I did was to get the 1uz with mid sump version. I used my own 1kzs auto gear box. Changed the rear drive shaft. No chassis mods, just engine mounts. Don't remember much honestly. But the engine got over heated on me and fried. I read in multiple forums about over heating issues but didn't had the time and stamina to work on it as I had much important things to do haha. Anyhow I went for 5vz swap which was again first swap in this model. Before 1kz, I swapped 1kdftv in this 4x4, very very new engine for its time.
Rest shoaib kiani can guide u more as he has 1uz transplanted his fj40. Thanks.