One of the artists for the game, Mark Van Haitsma, released character concept artwork on his website, showcasing some of the differences from the character artwork to their actual models. Sonny's spoiler folds were originally pointing down, but were later changed to point up. Additionally, Cortland's racing number was to be 4, but was changed to 191 for unknown reasons.
More content can be found in the localization files:
There could have been one more Piston Cup race called Pinehills International Speedway.
There could have been a race with Lizzie.
There could have been a mini-game where one can pave the road with Bessie. However, it was released in Java version of the game.