Hi. There is no mixing in the Blender file. If it doesn't match perfectly that's on purpose because when I printed this the pieces either printed too small or too large because the filament expanded in some places and shrunk in others. I gave up on trying to figure out why this is the case and just sanded areas down that were too big or used gorilla glue in areas that were too small. If you want the HD body in the Blender file, just select the piece you want and export it as an stl file. Its that simple. And its very much printable. There is literal photo evidence that I printed this just fine as have many other people. If you need help with how Blender works and how to export files here is a tutorial I made: https://www.youtube.com/watch?v=PdEUGXBdQmg&t=13s
I hope this helps.