Help modeling 3D printed replacement part.

Dear BlenderArtists community,
I have been attempting to fix a broken part for a friend. It is the front part of a vintage pedal car. I 3D scanned the broken part with 123D Catch and imported it into Blender. I was then hoping to design a piece to fit exactly to the broken part, and then 3D print it out. I would like to do something similar to what was done here. http://www.instructables.com/id/A-sandstone-block-built-from-lego-blending-real-o/
Please help if you have any ideas or suggestions…
Here is a link to the model…
https://drive.google.com/file/d/0B0j3WGD5eyXjVHlBOUtFSjNkWW8/edit?usp=sharing