If you're looking for "with ease" you could put in a SOHC diamante engine. Its the same with the exception of the pistons and cams (has 10:1 comp ratio) I think theres a small stud you need to gind off to bolt up the AC bracket.

Its rated for about 170 HP but I'm not sure how much of that you'll realize with the montero intake and computer. Tourque band will most likely be higher in the RPM range as well..Jason A used Diamante pistons in a rebuild and reported good results.

99 Gen 2.5, fixing blown head gasket
89 SWB- 33's, ARB Front locker, SR rear locker/axle, SR F brakes, winch, WST Offroad Armor all Around, 2.85 Aussie T-case Gears (SOLD)
Sold: (2) 95 SR's, 86 SWB, 90LWB, 91 LWB
-Can Change a timing belt in my sleep..