I just helped a touareg friend rebuild his 12HT, with a kit from down under. Quite affordable I thought, 1295 AUD including con rods, pistons, rings, all bearings, gaskets. For once shipping was reasonable, usually kills any dealing with Oz.
I was happy when it arrived to find all Japanese parts, steel reinforced pistons, Denso and other makes.
Abdellah was thrilled - he could only find chinese parts in Algeria.
Also installed new injectors and turbo. Turbo was Chinese but should do the job. Injectors that used to be impossible to find are now on ebay, with a choice of Denso or aftermarket, reasonably priced.
Myself, I am not sure I need a 12HT in my car. I have had many 60s with 2H and they were rarely short of power. If I was running through loose sand dunes more often, it would make a difference. For home use, being able to go 110 or 120 km/h on the highway is a good thing, rather than stuck at 90. But the car I have now with 12HT has its otiginal 4sp so I can't anyway.
Bottom line is seeing how much harder it is to find parts for 12HT than 2H I think it would be better to install a turbo in a 2H. Then not crank the turbo pressure up other than when it is really needed.
Touregs say 12HT is better than 1HZ; I dunno. They probably prefer the old style truck engine and no electronics, for obvious reasons.