Jazz would a PWM to analog converter work with the motors you currently have in place? As they are an off the shelf item and do come in many different voltage tolerances. That would save having to replace the servos. I do know that some are used with upgrades of older machines in the Michigan. As the servos are stil rock solid the electronics go to crap well before the servo ever does on many older machines. Seems like they cut the corners on the wiring and boards over the motors. That or the tech to make high quality motors had already come down to reasonable prices back in the 80's and 90's, when a lot of these machine were being made.

Good luck on the the rebuild and will keep watching. Now you have my son Mario reading up on Linux CNC (which is a good thing).