I have a mill that is just about like yours I wish the head of mine was like that but the base is the same. I put AC brushless servos on the mill, man is that thing FAST! It is 1.34 Hp per axis and I took the belts off the X and Y axis. I get about 500IPM and it will move a .00002 inc (only based on the Encoder,Didn't check to see if it was true). I also got a 10" 4th axis for it Nice mill, I think you are going to be happy with it!
These servos are ferrite brushed. Handbook says rapids are 400 ipm. Torque is 4.5 Nm, I think that's 637 in/lb. Hope that comes out to be around 600 Hp.
I printed out the manual and have read it a few times. Been reading forum posts ad infinitum. Now have I/O (Information Overload).
My integrator pal, the famous/infamous Mike Pearman of NC Repair, is coming over today to laugh at me. If I scmooze him right he might even help.