Yes I agree, it should be made right, its so close to being good and it is a very important thing to have control over the machine, especially big metal cutting ones.
Ive had a quick look through the machine books. Fortunately I have them. The DC motors have pulse coders and tacho feedback. Ive found the pin outs for the velocity control. I havent found any pin outs for the spindle drive. The servo drives are SCR. They give a lot more info than I thought they might.
It looks like main axes can be controlled by hooking up the DSPMC analogue out to VCMD on the velocity control units and then finding the old pulse coder input to the "position control board" and using that as encoder input.
The biggest drama will be figuring out the IO, maybe I just have to trace it back.
Hood, you took out the motors and drives and put in new ones, was that because the old ones were dead or did you just want new ones, or was it getting too hard?