Danny put a cherokee trans in his Montero Sport, I think in Dannytuned SAS write up he went into detail about the swap. The Cherokee AW4 has lighter duty internals than the Montero AW3 from what i hear. Which would make sense since the Montero weighs a lot more than a Cherokee, don't think it would cause any issues. Otherwise it's the same transmission basically.

One of my friends swapped a late Cherokee AW4 into an old Comanche pickup that originally had a manual trans. He bypassed the computer with a manual shifter setup which you can do on pretty much any of those types of Aisin Electronic shift transmissions. So you could do the same in a Montero if you wanted to simplify things.