why a Ford 9"?

The main reason they are used is because, as my buddy used to say about Chevys, "everybody runs 'em because everybody runs 'em." When they are readily available the price goes down. Two important factors when trying to build a fast car. Then the more people that use them the cheaper replacement or upgrade parts become. I know that I could go to the local wrecking yard today and get a Ford 9" to haul home. I doubt that I could find a 8-3/4 available in the state!