I run a 2003 Acura v6 it makes 235 lbft of torque at 3500 rpm and peak horse power of 270 around 5000 rpm. The engines are plentiful J32 series 3.2 liter. I went with this as the engine is powerful, cost effective about the cost of a VW 1915 cc. parts in the after market are plentiful. - the only draw back to this choice is that you will have to build a trans with racing gears. Mine is still stock with a supper diff but its not if it will break it is when.
The VW v6 you are asking about makes about 170 horse and I believe it is a cast Iron block where the Acura engine is all aluminum. So if you had one you could in theory make it work. You can go to
www.kenedyengineering.com and look at the list of adaptors they make.
The echotec engines seem to be another great alternative as well as the Subaru engines. Try to stick with more common engines as part as less expensive and more readily available.
Best of luck whatever your choice.