Hey friend, the x-carriage pictured here is Prusa's original carriage. It lacks dedicated fan mounts, and my fan duct and bracket replace the normal belt clamps one would normally use.
Prusa's original files are on github, at https://github.com/prusajr/PrusaMendel/
I also suggest looking at Greg Frost's improvements to Prusa's original designs, also on github: https://github.com/GregFrost/PrusaMendel
And, there are other designs here on thingiverse that are based on the above two designs.