That's a fantastic resource!the guys in Russia in August 2011 have already installed an additional fuel tank on the Prado 120, if you need any spare parts, I'll try to find them.
If you need a translation from Russian to English, I will try to translate it.
LINK:
Установка дополнительного бака на 120-й с двиг-м 2TRFE
Установка дополнительного бака на 120-й с двиг-м 2TRFEprado-club.su