Thanks for the insights! Good post! Didn't mean to turn this into a 1KZ vs 13BT discussion but thought that the 1KZ is a good reference point here.
Agree on superiority of 13BT which is essentially the B series engine with turbo and direct injection. All B series engines will get you to the moon and back while towing a tank and 16 passengers on board...
I have seen variations in 1KZ particularly converted 1KZs and my opinion on speed would be same had I not driven the black Wrangler done by Farooq Awan. Soft top with 1KZ-TE, 4.1 diffs, a prado auto gear box and rear disc brakes. I tried to test drive the car twice and essentially gave up both times as I felt the car was simply dangerously fast. Stock 1KZs Prados typically have a 4.3 ratio. I have driven other Wranglers and TLC 70s with 4.3 (or higher) diffs which are powerful but not exactly very fast.
The 13BT on the other hand (like other B series) typically runs on 4.1 diffs which probably contribute to its being faster in stock factory settings. Also as you mentioned with the ruggedness of the engine, you could can comfortably overload the turbo and pump settings with good returns.
All said in done, if I were to build a diesel wrangler or 40 series today (or for that matter any shortish wheelbase 4x4) I would put in a 13BT. Hitches would be the weight (I think its significantly heavier than the 1KZ), the cost (at least 50% more than 1KZ) and issues on parts availability (manageable but comparatively expensive). But then again why would I do another diesel 4x4 in this day and age?..... for the reliability perhaps!