well any diesel jetta should have a nice little diesel in it, they were pretty reliable and great on gas. check the scrapyards and classifieds. not sure about what trans you could mate to it but the broader point i was making is that the indirect-injection diesel engines found in passenger cars would be more suitable to your conversion because they are lighter in weight, quieter, reliable, and also rev higher than direct-injection industrial engines.

6.2 is a good engine but it is a huge jump in weight and you definitely will have to change the whole suspension and driveline. there are members on this forum that have done the VW jetta engine conversion to various vehicles, a forum search should bring up those threads. i'll do a quick look and see if i can point you to someone.