Even if you want to just import cars it takes a little creativity. Basically the steps are the same as these:
http://wiki.vdrift.net/index.php/Creating_cars - but, in the step where you create the models, you import them from another game. You can use the dof2joe utility for converting the models to VDrift format from the Racer format. Or you can get some software like zModeler which will import some other formats and export to Blender, where you can use our .joe export script to get them into the game.