What is the largest domestic factory gasoline auto engine ever made?

The title of "largest domestic factory gasoline auto engine ever made" is generally attributed to the Cadillac 500 cubic inch V8, produced from 1968 to 1970. While other engines might have had slightly more displacement in niche or experimental applications, this engine was a mass-produced, factory-installed option in a passenger car (the Cadillac Eldorado, among others).