I used an 11×15 cake pan and filled it with two cake mixes and baked until the tooth pick came out clean! Then I froze the cake to make shaping it easier. Once the cakes were frozen I cut them length wise and then made two exact match rectangles (approx. 5×14). I cut off the edges and made everything "square". Then I stacked them and started the shaping of fire engine cakes.
I cut the top piece into thirds and then split and stacked them as necessary until I got the desired shape. Once I got the desired shape I used butter cream icing to fill the spaces between the layers and "glued" all of the sections together. Next cover the outside of the truck with a heavy coat of butter cream and smooth perfectly. Then I used fondant (premade) icing, colored using Wiltons color, rolled to the proper size and covered. Use a flat edge to smooth and press into place and then cut off any extra with a pizza cutter.
Decorate to your idea of a fire truck, present to your child, and cry when they destroy your creation!