Hi Tom,

First the wheel in a box looks like it's a rotary table of some kind which is used has a 4th axis. This will be or would have been connected to drive of it's own or shared with an existing drive by swapping cables of the axis thats not used when operating the 4th axis. This is a common way to keep costs down.

Regards the electrics what exactly do you have.? Take good quality pics and post.

To give an overview then in general you have individual per axis Drives to control the motors which often connect to the parallel port using a breakout board (BOB) for easy connection and some protection from damage.
There are multi-axis boards available that combine both drives and BOB but these tend to be cheap lower quality and unreliable, best avoided if you want a stable machine.

The motors are nice units and quality from a German company today called ISEL. They probably did use bespoke multi-axis board thou it would have been a quality unit. To be honest I think you Grandfather probably modified or used parts from a ISEL or ISEL Techno machine which where decent quality machine.

If you matched these motors to modern drives then you'd have a nice setup, avoid the combo boards unless you use Gecko G540.
The Chinese drives like M542 leadshine copies are very cheap these days and far superior to most Combo boards with not much cost difference. They out perform most all-in-one boards by some margin even some of the better one's like Roy's at DIY cnc.
Breakout boards are cheap enough and often you'll find kits on Ebay with drives and BOB.

Regards software then you'll need a CAM (not CAD but CAM) program like CAMBAM to generate G-code from your CAD files and then you'll need CONTROL software like MACH3 or LinuxCnc to control and run the machine.
CAMBAM has a limited free version and the full working version isn't expensive.
MACH3 is by far the best option controller wise for a newbie but it's not free. Linuxcnc is free but not so intuitive and user friendly to new user and hasn't got the newbie friendly user base backup Mach has.

There are other options like USBCNC that combine BOB and control software and use the USB port not parallel port for motion control which you could take a look at if you plan on using a Laptop.
Don't try using MACH3 with a Laptop has they don't mix well without a separate motion control card.

Hope this helps and post more pics of the electrics you have.