Here is the mill with the 4th axis modeled in Alibre. Although Alibre can import the older models designed in Solidworks directly, the assembly files do not translate the relationships between parts, making it less useful. The practice in a new cad system was helpful as well.
The main reason to do all this work is to finish the design and installation of homing switches. With smaller stepper based system, these are not required for a mill without a tool changer. I am working on a tool change system, manual at first, and later automated, so the switches will be needed.