This was a common-ish option for V6 Toyota 4runners, when I had mine I researched it some but I read reports of guys spending up to 11k and still having over heating issues and some that turned out successful but at that sort of money I gave up, also as Dave said the 3.8 buick V6 is/were a shit motor.
A friend of the family had a V6 D22 Navara STR dual cab waaaaaay before I got my diesel one, he said it went well but was very thirsty and eventually got rid of it, it was immaculate too, he offered it to me for the traded price he was gonna get but I didn't want to buy a V6 one. A reasonable bit of research will show the Nissan V6 to be quite a good engine compared to the Commodore one and yeah Marks Adaptors would be the most likely company to offer a kit.