I also have a CX601 mill and have been (very slowly) converting it to CNC. I did succeed in converting it but there was some slop in the Z axis and ended up mothballing the project (for years) and am coming around to try to solve that issue. I ordered the ball screws direct from china. Power supply, steppers, drivers, and other electronics from US suppliers (some components like bearings were ordered from motioncanda dot com. The rest I made either on the mill itself or my lathe.
The conversion kits linked by gerritv, david_r8 look pretty nice. And honestly, unless you really like having to solve problems these might be a great way to go. On the flip side, I learned a ton about bearing loading, ball screws, thread pitch & torque, different screw support configurations and their impact on accuracy, rigidity. Hours sunk reading books (Mechanical Engineering Design & Machinery Handbook were helpful) Even spent some time with a NTN bearing engineer on the phone discussing matching bearing configurations, pros & cons.. and the list goes on. It was and still is a rewarding process.
The rabbit hole is pretty deep depending on what you want to do and what you want to get out of it.