What Mitsubishi engines bolt up to our transmissions?
Luckily high speed cruising
Luckily high speed cruising is not really a requirement as speeds never go above 100 kph where I'm from but I frequently need torque low down in the rev range for steep hill climbing. The mountains are high altitude here as well with some of the passes being over 3500 meters so the turbo sounds nice.
But I didn't think about the gearing issue, and you are right on the limited options when it comes to the IO. The Mitsubishi ASX and outlander that the 4n13 and 4n14 engines are from seem to have decent acceleration, but those have CVT's so their gearing is completely different. I guess the other option is to add a turbo to my 1.8 MPI engine and just size it so it spools up nice and early.
This is coming from the fact that I was unable to climb a paved hill last weekend without being in 4lo due to the altitude. And that caused a problem because the hill had a sharp curve in it, which sharp paved curves and locked center diffs don't mix well. I'd like to have more torque to eliminate issues like that. The other thing that is tempting with diesel is it is 50% cheaper than low grade gas here and 60% cheaper than high octane.
Syndicate
I can't answer that question - BUT -
I'd strongly suggest you thoroughly research the idea before moving forward - I'm not a lover of small diesels, and there are very few circumstances under which I would consider a petrol to diesel conversion.
First my experience with diesels is primarily with Mitsubishi products primarily the L200 & L300 models - performance of the naturally aspirated versions is absolutely dismal, the turbo charged versions are what I would consider barely adequate, I've also driven a couple of the full sized turbo diesel pajeros and those, whilst they have been passable have been nothing to write home about, they have power low down, but "run out of puff" quite early compared to a petrol engine and in my opinion, don't make for good "high speed cruising", they are economical but not enjoyable.
Now, what I'm describing here is vehicles that left the factory with the diesel engine and presumably optimal gearing for that diesel engine, which is something that is very difficult to do with an engine swap.
Petrol engines deliver their power at higher rpms than diesel engines, most petrol engines, especially the smaller ones like the 4G9x series will happily run at 5000+ rpm all day long, and the average diesel will be redlined well below that, you pretty much have to "re-gear" to get a petrol to diesel swap to work properly, and you don't have much choice when dealing with an iO.