Have you submitted your site/sitemap to google? It looks like you're doing a little bit of keyword stuffing on the front page - i'd nix that.
I've just done a quick sweep of the site, but I'd start some social media outlets like twitter and facebook - also look to discussion boards where you can start interacting with your audience and building links.
There are lots of things that go into SEO besides just the backend stuff but it looks like you've got a lot of content that's optimized.
Looks like you're using multiple <h1> tags when the <h1> tag should be reserved for the main title of the page and the keyword you want to rank for. The rest of the subheading should be <h2>
You have no meta description of the pages either, so start writing some up for those and include your keyword within it.
I'm not entirely sure the scope of services you provide. I mean, I can tell you export - but do you have an inventory at the moment? Sometimes having a database of inventory and information on each car can help, especially because it gives your site more content - then develop ways to share the information by adding in social shares (an app of some sort on the site) and start tweeting the inventory on your social networks.
Obviously this is just a real quick snapshot, feel free to PM me if you have additional questions.