The replies to my inquiry were all appreciated. To sum up:
General motors engineering division developed the motor and farmed it out
to Buick. Buick refined the engine and it was used basically unchanged in
the Olds and Pontiac line-ups.
The design was then sold by Buick to Rover. From there it made it's way
into many BC's. One response indicated that this engine has a descendant
available in the current Land Rover line.
Thanks again all. I'd really like to own a TR-8 some time. For now I have
enough projects though.