Is it possible to create a Brand -> Model Taxonomy

Hi,
I would like to create a Cars dabatase. For this I will need to create taxonomies for Brands (Ford, Peugeot, Toyota,....) and models (Eclipse, Focus, Navigator,...). Each brand has its own models.

This could be made by creating a single vocabulary where brands are parent of model terms, but this will be very long, due to many brads and models.

Other option could be creating a vocabulary for brands and other for models. But this could lead to errors since there will not be relations between brands and models, i.e. if I select Toyota, the selection of Models will not be reduced only to Toyota models.

Is it possible to create relations between terms of separate vocabs?

Is it possible to create AJAX form for the user to first select Model, then Brand?

Any help would be appreciated.

Thanks