I bought this drive on the bay:
http://www.a-m-c.com/download/datasheet/b100a40ac.pdf
It's for a 10 horse brushed DC spindle on a Matsuura bed mill using a Galil card and Camsoft refit.
This thing will likely have over voltage issues slowing down. On page two of the manual above, and on the dirve itself, it looks like you can just use a resistor. I have no idea what size.
AMC also shows these
http://www.a-m-c.com/download/datasheet/srst.pdf
Are these necessary for this use?
Karl