Thats not entirely true but revs arent really important while driving an SUV, its the midrange toqrque that you need to get it running 
From what I've heard, the engines I mentioned will give you around 7-8km/l, but that also depends upon the condition of the engine and your driving style.
My friend had a 1996 Pajero Exceed V6 and it was absolutely great! You can contact Mr.Hanif Bhatti aka LIBRA, he has a lot of info as he's maintained his "Becharo" very well 