You might find you want two different cars rather than one. I have no intention of trying to upgrade/swap my 1HZ for a turbo. Why? Well I think of it this way. I have a diesel 4x4, because I want to be able to go offroad. The fact is, if I fully load my HZJ80 with gear and five passengers, I can still stick it in low range, and from a standing start crawl up basically anything. It has enough low end torque and gearing to pull itself up, as long as you can find traction and don't roll/beach it, you're set. If we had altitudes in Australia high enough for a naturally aspirated diesel to struggle I might feel differently... but we don't. With the factory HZJ80 gearing, I'm not convinced more torque off road is useful, the 1HZ has enough, any more and you're really just multiplying the chance you'll break something IMO.
Now, on the highway my HZJ80 isn't the fastest, but I don't think it's exactly "slow" either. I'm not going to win too many drag races, and I can't always keep 110kph up a really steep hill fully loaded, but I can at least keep 90 if I'm not half asleep. So if I wanted something that was "faster", I'd really be talking about faster acceleration, higher top speed. But am I still describing a 4x4 at that point? Each step to "improve" the power of the HZJ80 comes with drawbacks, not just cost to modify and reduced resale value, but new maintenance headaches, more potential things to go wrong, and a lot more trouble sourcing parts or getting work done on it. I like the fact I could drive my HZJ80 across the Simpson desert without refuelling, with only basic tools and a handful of spare bits and bobs. That's what makes me smile about my 80. I don't want to mess with that pushing for better street racing cred.
IMO, the ideal setup if you've got the need for speed is two vehicles, one the most bulletproof, dependable 80 that can be built. The other one is whatever the hell else you want to drive places where you want to move a bit zippier, be a bit more comfortable, etc. It may still be a 4x4. It may even still be a Landcruiser, possibly even an 80, but don't ruin the reliable rig trying to turn it into the fast one. You'll end up spending a fortune, and left with neither.