Step 1: Sketchup
You can download the sketchup file here. You need the Google Sketchup program (free version is enough) to open it.
Step 2: Cutlist diagram
Step 3: Making the engine head
Step 4: Making the rooftop
I also used the router to cut a 1/4" groove along the inside of the arcs and the side rail so that the roof board can fit in.
Step 5: Bed body
Do not throw away the 2 cut-off pieces from the window - they are used as the 2 shoulders for the toy chest.