! Update Apr 11, 2015 !
New files and a second version. (http://www.thingiverse.com/thing:766843)
Didn't like the original x-carriage.
Added a screw mount for the endstop on the x-carriage by eMotion-Tech (http://www.thingiverse.com/thing:119616/#remixes) for Prusa i3 Rework.
One for T5 belts and the other one for GT2 belts.
The 625 bearings for the X-belt and the Y-belt needs a small m5 washer on each side and then one large m5 washer each side like:
(large washer - small washer - bearing - small washer - large washer)
Might needs some washers between bearing clamp x, y belt holder.stl and printbed lower carriage.
Added a longer bearing clamp x (bearing clamp x longer.stl) and y belt holder.stl (y belt holder longer.stl) instead.
A K8200 or 3Drag and some extra screw, nuts and washers (m3, m4, m5, m8)
Longer feets (http://www.thingiverse.com/thing:719859).
Optional (probably best to get it):
2x Springs for the backlash on (z_holder_endstop.stl) and (z_holder.stl).
Nema 17 stepper motor.
M8 threaded rod.
GT2 belts and pulleys.