Trying to use the original Fanuc hardware is difficult if not impossible. I gave up and went to all new hardware on my project, the only thing left in my lathe that says Fanuc on it is the spindle motor, and it is being powered by a quality VFD now.
Use only one motor for the Z, trying to sync two would be a nightmare.
On a machine that size servo motors are the only way to go. DMM servos would be my preference, I've had good luck with them. DMM | AC SERVO DRIVE | AC SERVO MOTOR | ROTARY ENCODER Pricing is very competitive with larger stepper systems, and they are much more robust.
The DMM servos will take a step & direction input, so can be used with just about any control that you choose.