I have made a few automobile cakes in recent years. Hubby cuts a thin board and i purchase wooden tires from woodcraft dept at Hobby Lobby. I put a dowel rod through the holes and wrap the board in board paper & glue the dowels to the bottom of the board with wood glue. I cover the wheels with black fondant and build & carve the cake. I just make sure recipient knows the tires are not edible.
If possible, i get pics straight from the front, back & sides & print them out on large paper(i work @ a print shop) and cut out each piece & use this for my template to ge the shape right.I use buttercream, not fondat for my main cake coating.
Here is a link to the cars & truck cake pics I have made.
Hope this helps!