[TimG]

The W31 option was not available on a 442 due to the engine being a 350 cubic inch motor. The W30 was only a 442 option and included the high performance 455 engine among other things.
You'll never see a W31 442. They are good cars, most of the 442 neat stuff in a small block car.
Others on this site know lots more than me about Oldsmobiles. I love them, but don't have a tremendous amount of Olds knowledge.