I don't know how much help I can be with the mechanics of your machine. About the only mechanical thing I did was change the Y angular contact bearings as they were bad. Everything except the Allen Bradley controller that came on the machine is still there. I am even using the same servo driver, just supplying the 10v signal with a Pixie board (no longer manufactured). The servo motors have tachs and encoders. The tach are used by the ServoDynamics driver. I don't know the resolution, I let Mach figure that out. You can tell Mach to move the machine 5" (or whatever number you want) and after it moves you tell it how far it moved and Mach will set the proper resolution. I belive the servo motors are ServoDynamics MT30U4-42.
I have a 5BVK that i am working to retrofit. I'll look the motor model number for you first thing monday, i do know that they where Baldors, and they had encoders on the back of them (again, i'll grab model numbers for you). I have been draggin my fee on this sooo much it is kinda sad, might do more if i have someone going through the same things.