I found some model kits on eBay that are half scale. There is a Horseless Carriage and a Surrey. I put the links to my gallery images below. I have plans for these and have also purchased a Hansom Cab that hasn't arrived yet. All were fairly cheap, too. Search on eBay in model kits for MOD-AC
Horseless Carriage --
http://www.greenleafdollhouses.com/forum/index.php?app=gallery&image=86610
http://www.greenleafdollhouses.com/forum/index.php?app=gallery&image=86611
Picture of the real George Selden and his invention --
http://www.greenleafdollhouses.com/forum/index.php?app=gallery&image=86612
Surrey --
http://www.greenleafdollhouses.com/forum/index.php?app=gallery&image=86613