@RichardHyland, etc. I develop as well as market, you're going to find it awfully difficult to find a WordPress theme or the like that suffices for all of the dealer website requirements out there today. Forget out of the box solutions (they aren't going to work for you and the support is generally shit), you'd be smarter to go with a theme that was developed by someone in the automotive industry itself, such as what
@Chris Cachor is offering and I have absolutely no connection to Chris at all.
That said, if you're looking for something basic, which isn't really going to help you with most users today (they're looking for more), there are plenty of amateur, poorly supported options at the likes of
ThemeForest, etc. However, unless you've years of experience using WP, you're probably going to struggle setting up and maintaining a site using these types of themes. Mind you, none of these developers truly understand the requirements needed to facilitate a proper inventory-based, dealer website.
IMO, this is why groups like
Dealer Inspire,
DealerOn, etc. have been incredibly successful. They get it, you can have all of the flexibility of WordPress with customization and back-end / API hooks. Their flexible themes, widgets and components are developed with an understanding that requirements change. It's what you pay for with them. You're not going to get that with out of the box solutions.