Let me share my experience with you:
I own a Mitsubishi with similar but not the same engine (mine is a turbo charged 4g63, sports car). I am on my fourth engine in the 11 years I have own this car. But I will tell you that this car is the love of my life!! It is probably the fastest car in Bongo, and I am not finished with the power build up, yet!
Also, I have recently converted our Pajero track, froma diesel engine to a Toyota petrol engine. And 'am very happy with the change! The Pajero engine was just too unreliable. On the other hand, the 3Y Toyota engine installed is known to be very reliable. It is the same engine used in Toyota Stout and Hiece (dala dala vipanya).
Now about RVR; Most people will tell you RVR engines are piece of shit, but there is more to it. I think we are not maintaining this engine properly (like changing timing belts, etc). Sasa mimi kwa ukweli sijawahi kuwa na hiyo gari, lakini ukweli nikwamba a Toyota engine is likely to be a more reliable engine that most Japanese car out there (Honda probably is the best, but they are too expensive).
So if I where you, the first thing I will do is research what engine match the power band of your exiting engine, and talk to those who have done it before in order to make the process easier. The biggest challenge is on matching the engine mounting areas of the new engine to the location where the old one was. But this can be done. The next biggest challenge is to get the control box of the new engine to work in your car.
Do your search, I can help you if you need more research assistance. Pia, mafundi wangu wanaweza kukusaidia...
Mbongo mwenzio