RCaffin, just a suggestion here, SCR motor controllers are not the way to go anymore. They are hard on brushes. I just went thru a dead spindle driver and replaced it with a KBRG-255 and what a mistake. Motor heats up way too much and is loud. It used to be quiet and ran cool even after a whole days work.
So my suggestion, is a mosfet or igbt motor control.
If you are using Mach3, check out Advanced motor controls. PWM in and pulsed DC out to regulate speed and power.
Also to determine the proper size of drive you need, you should check the actual output of the KBMG at full speed.
Just because the motor says 180VDC, it doesn't mean that's what it was running at full speed.
AL the man, can make more sense of this. He'll steer you in the right direction if he sees this post.