I find most of the information out there about this engine to be inaccurate. Almsot avery one of them gets the facts about the Chevrolet and GMC engines wrong, especially as to who made what displacement, and in one case, listed a Buick V6 displacement as the Chevrolet inline 6 displacement. Looking at the engines themselves, I see very little in common with the Chevrolet, other than the fact that they are both inline 6 engines and both have 4 main bearings. The Toyota looks more to have been copied completely from the GMC, the oiling system is similar, and head is an almost spot on match other than the port layout(look at the chamber and valve layout, it does not match the Chevy at all).
As far as being "built under license", that could be anyones guess. I do know that Toyota got their start in the auto business importing Buicks to Japan in the '20s, so it is possible. Also, GM and Toyota have had a long standing working relationship until just a few years ago.
