What test case yaar! Really! The people who are doing the conversion have done hundreds if not thousands of successful conversions of Toyota engines in Jeeps. The guys making the adapter plates have been doing Jeep Dana/spicer/aisin to Toyota adaptions since 1983. The guys wiring it have their computers honed in to tell what their engines had for breakfast last week. Yes, since its a Pajero conversion, things get a bit tighter and you may have to revise some stuff a few times to get the spacings right. Otherwise, if its Mitsubishis and not Jeeps it doesn't make anything all that different.....
Yes, things can still go wrong, but come on! Things do go wrong, even in perfect conditions. Robby Gordon or BJ Baldwin can start the biggest races in the world and retire 5 mins later with a blown transmission which cost $60k. Well maintained UN Land Cruisers can stop at the side of the road and need to be towed back. You try to do your best, but If a converted car stops at the side of the road, its not the first nor the last. You learn from your mistakes and you move on and try to do better next time. That's just the way it goes...