Dynomotion Kanalog/Kflop boards might be a good choice. Galil Motion Control products would work very well also and would be my choice for this project.
The tachs connect back to the servo drives so that they know how fast the motor is turning. The motion controller sends a +/- 10 volt analog signal to the drives, and receives feedback from the encoders. It sounds like you need at least an 8 axis card given the number of servo driven devices you have on that machine. The good news is that it sounds like they left the main components intact.
As far as off-the-shelf software, I have no idea. If you can make it run on standard G code, then Mach3/4 might be an option. If you are a programmer it wouldn't be very hard to write your own software, if you're not, then it would be a bit of a learning curve. Sounds like an interesting project, I've been wanting to do a press break. I might be able to help you a bit when I get a couple other projects out of my hair, just finishing up the full 4 axis profiling integration on my CNC software. Then I have to get my CNC lathe on line, that should happen in the next week. But a word of warning, Mach3/4 and I don't get along well.