My most recent retrofit is an old Dahlgren System 300z. The guy dropped it off at my house for $100. It's a 3-axis engraver with a work area of 12" x 24" x 4.5".
It sure isn't pretty and it hasn't been used in 10 years but not bad for being delivered to my house for $100. It's built heavy and the rails are all in good condition.
The old controller box box is rated for 500w with an intel 8086 and 65k of ram. It has separate cards for each motor driver and the spindle. The motherboard is labeled 65v and the components are rated for 100v. I'll be replacing all this with some more modern drivers and creating a custom controller for it.
Each axis, the spindle, and limit switches are nicely separated with plugs for each.
The stepper motors are Powermax P22NRX8 unipoler steppers with a rating of 3.3A.
I'm unsure of the spindle motor at this point but know it's a 3 phase BLDC motor with hall sensors for feedback after doing some tracing of the pins on the driver card.
I got it working:
Some more over at my blog www.codelv.com/blog/search/?q=engraver