OK so I answer my own post, how sad
I have CNC'd the Myford and turned a few test parts.
I made a mounting plat to sit above the slide screw. I inserted a timing belt pully between the slide crank. A timing belt connect to a stepper mounted on the plate.
I used some old timing pulleys and belts recovered from scrap.
I think the pitch of the slide screw is 2mm. This is my X axis
For the lead screw, I made a mounting bracket to fit on the drive chain arm in the gear housing. I coupled the motor with the lead screw using standard Myford gears 20:60.
I think the pitch of the lead screw is 3.14 (8tpi). This is my Z axis.
I am quiet happy with Z axis but the X axis is not calibrated correctly.
I seem to have a 0.3mm error in about a 10mm movement on the X axis.
I think my problem lies with the timing pulleys I used. I don't know their correct ratio so I measured them with a digital vernier and used that as the ratio (11.4:21.4)
I know the ratio sounds wacky.
Is is ok to measure ratio on time gears like this or can you simply count the teeth as you would on normal gears?
Maybe I should just dump the "scrapped" pulleys and buy known items.
Will post some pic's some time.