re: "red" fire truck from cars

http://crazycakes.canadianliving.com/entry/2915395?offset=508&sort=time+DESC Here is a great version of Red

Here is a tutorial of sorts using a half sheet cake…which is the basic size you were talking about. http://dozenflours.com/2010/01/fire-engine-cake.html

I hope this helps! But you are on the right track! =) Good Luck!