Appreciate the reply.
I've come to the same conclusion that boring out my current engine is not an option. Additionally a 5L with mech injection is not worth finding/importing for marginally better performance.
My plan as of right now, I am planning to rebuild the 3L and put on a turbo kit. Northwest Toys out of Oregon sells a lot of stuff, but they charge an arm and a leg. I'd be in like 9 grand to rebuild, modify my pump, and use their valve and turbo kit. That's if I do everything myself.
I'm going to call HD Automotive in Brisbane this afternoon. They have a great reputation with their kits, and they sell a rebuild as well. For about half the price.
Hopefully they will be willing to ship internationally. Their website says they will ship via DHL.
Planning to pull my engine Friday. I'll post pictures.
Toyota turbocharged the 2L and you can read about the 2L-T routinely cracking heads on here and any other owner forum. They never tried it on the 3L or 5L. Indirect injection diesels concentrate heat in the pre-combustion chamber of the head (this is where the compression occurs, and where the combustion at least starts), and the head is fundamentally weaker because it has to accomodate the pre-combustion chamber. This seems to be fine on a normally aspirated and low stressed engine - the legendary reliability of the 2L, 3L, B, 3B, 1HZ testify to this, but once you turbocharge it you have an engine which is very vulnerable to overheating - a poorly flowing radiator, malfunctioning viscous coupling, coolant leak etc can easily lead to an overheat and on these engines, that very likely means a cracked cylinder head. This would be fine if you had a cheap turbo and a throw-away engine, but for 9k USD??? That's an outrageous price. Practically double what I paid earlier this month for a complete, low km 15B-T engine with all accessories that came straight from a Japanese military vehicle (given I am in SE Asia where availability and shipping are not an issue).
Sure you will find stories of people running home-turbocharged 3Ls, 3Bs etc for years, but that's survivor bias. Just try searching for cracked heads on 2L-Ts, 1KZ-Ts and you'll get more threads than you can read - especially on non North American forums. Same on user-turbocharged 3Bs. Here in SE Asia the 2L-T and 1KZ-T are not taken seriously as a Landcruiser engine for anything other than road driving. The 1KD however is very popular (though a much more complicated install) and I agree, an amazing engine, though it did have teething problems. The direct-injection B engines are the ones to go for, though they are probably too heavy for a Hilux Surf and are fundamentally lorry/bus engines which feel quite different from the car-like 2L/3L.
I would just open up the 3L and make a call from there. Almost certainly all the pre-combustion chambers will be cracked. If the head is also cracked then you're into serrious money vs. risking Chinese components to keep it running. All being well, I would just do a nice rebuild on the 3L with a local machine shop - it's an easy engine to work on with great part availability (globally). Then just enjoy the slow 3L experience. I did a 4+ year, 150,000 km road trip in a Hilux with a 2L and, yes, they are slow (I once got pulled off the German autobahn for driving too slowly

) but other than that they are great engines.
If you're willing to drop 9k on it then you have a lot of engines to look at there. IMO the only decent engines they ever put in the second and third generations of Hilux Surf were the 3L, 3RZ-FE, 5VZ-FE and 1KD-FTV. I would be picking from that list. North America is, surprisingly, about the only market where the 5VZ came with a manual transmission and that would make a very nice on- and off-road vehicle.
Oh, and I forgot earlier, I have driven a 5L - it was in a friend's LN168 off-roader and is/was turbocharged. It really went nicely but had a short life before the overheating problems started.
EDIT - just looked at your profile picture more closely and see that we are probably talking about a JDM LN10*, so ignore my comments regards a Hilux Surf.
EO