I keep meaning to do a proper write up on my conversion but never spend the required time.

The quick description is:

I replaced everything electrical except the spindle motor itself. I got a new AC to DC motor power and speed control.
I replaced the stepper motors with new nema 21 stepper motors - they bolt into place without modifications. This gives the machine more power on the axes over the original stepper motors.

I used cheap stepper motor drivers but even slightly more capable drivers are available today for relatively little $ . In my case the cheap ones (TB6600's like these https://www.amazon.ca/TB6600-Stepper...7B9ZQF5D&psc=1 ) have been working fine, haven't toasted one yet.

The place I spent a bit more money was on the interface between the PC and the machine. I bought a Mesa 7i76e card 7I76E picture, which is an ethernet connected card that does the step generation on board and is compatible with Linuxcnc (which is free). This card is awesome (no affiliation, just happy!), I have one on my mill as well which was also a deciding factor (familiarity - I only need to learn one "ecosystem"). I choose it as I can easily connect a newer PC without touching the machine, and its not a PC card like PCIE or similar so no PC obsolescence issues there - wired Ethernet looks to have a fairly long life ahead of it, and finding a surplus PC that runs LinuxCNC well is getting easier.

I did spend a good amount of time on the tool changer, but that is due to my choosing to use a stepper motor to replace the DC motor that was on it originally. It actually an ongoing issue as I haven't spent any real time trying to sort it out. I could probably figure it out if I would just set my mind to it instead of choosing to go have a beer instead and read forums:cheers: