I have a 2UVRC that was NC'd way back by Tektronix. It had a custom Tek controller, NC400 Contrave drives and DC servo motors. I replaced all the motors and drives with Emerson servos/drives that take step direction inputs and control it w/ a PC. My spindle is driven with a VFD.
If your drives take step direction inputs then a PC should work just fine. If they want analog signals I think you run that with EMC and some controller cards off a PC. You can find some info with some searches.
I just recently got my mill running, and it sure is fun! If you have any questions let me know. I'd be happy to help if I can.