Shop built 4th Axis - Planning

I've got my vertical mill retrofit making chips. (http://www.cnczone.com/forums/vertic..._retrofit.html)

I bought the drives used from ebay and they came in a set of 4. They are AMC B30A8 (30A peak, 15A cont, 20-80VDC). So now I have a 4th drive sitting in the cabinet ready to go for a 4th axis.

I have ~5" of Z travel plus the manual knee.

I'm thinking about a 4th axis with a face plate that could accommodate faceplate/custom fixture work, a trunion style table, and a 2 or 4 sided tombstone fixture.

Questions / areas for research:

Motor specs to match drive?
Gear reduction?
Belts?
Harmonic drive? Can I have too much gear reduction (100:1)? Will this be too slow for 4th axis contouring.
Bearings in 4th axis headstock and tailstock?
Brake needed?
Encoder?
Software?