Stick with the Mitsu 3.0 variants, the best one to get a block and heads from is the Diamante. Most powerfull of the 12v 3.0's PM lordtrunks and he can get you pointed in the right direction as far as years and what to expect with the swap. it's pretty straight forward.

If you're feeling nutty and you know a bit about diesels you can swap JDM Pajero diesels pretty easily but it'll cost a lot more 3-4k.

1999 Montero SAS'd on Kings and stuff

1998 Montero trying to get a V8 Swapped