Also - take a look around insiderpages.com, citysearch, dealerrater.com, yelp, and all the countless listing services to see how your dealerships are listed. I literally have 15 place pages I have suspended for Google pulling in an indexing different locations. We are a Chevy store and one of those listings was for Jerry's Chevrolet, Geo! GEO!!!! How long ago was GEO???!!!?
Marc makes a solid point here: If there is conflicting information found on other online directories, it could potentially unwind the process.
Surprised to hear that snail mail is not an option for you, as we take that route when doing directory site submission for our clients. It's a tiny postcard that can easily get lost though.....
Best of luck to you!