After you have that installed go to the page where you can add custom code (I think it's under settings) and add the following;
The first piece (the css) hides the body style selection from the search form. The second piece (the js) tells the page to automatically select 'van' as the body style.
To create a search for cars you would add another custom code block and change the word 'van' to 'car' and then tell it to output only on the page you want to search cars on.
Hopefully you can use that to create your custom search until we have an option in our PlugIn to customize the searchs.
Let me know if that works.