I don't know much about the Montero, but if you have a selectable transfer case and not full time AWD, you can generally remove the front axles. The cleanest way to do it would be to swap in a pair of axle stubs from a 2WD Montero. The dimensions should be exactly the same. Just make sure you buy them with the ABS tone rings (assuming you have ABS) so that your ABS continues to function properly.
I'm assuming you could also delete the front driveshaft and differential as well. Without the front axles, you will have a 2hi, 2hi, and 2lo through the transfer case. :coffeedrink: