Take a pick!
There are lots of options, but the biggest thing will be are you going to stick with a Parallel Port, or go for USB/Ethernet with an external motion controller. If you go the latter, then you have to ensure it's got lathe functions, as not all motion controllers support things like threading.
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To give you an idea of options/price ranges, it varies from cheap BOBs on ebay that will connect to a parallel port, to full blown motion controllers/BOBs like those from CS-Labs or Dynomotion.
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Personally I use Dynomotion KFlops with a mix of Kanalogs, KSteps and Konnect expansion boards, however I can justify the expense, as my machines are making money reguarly. Also with the IO being 24V, it eliminates issues with interference causing false signals that you can experience with poor wiring when using 5V IO, as per most more hobby grade controllers.
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For more hobby use, personally I'd recommend an Ethernet SmoothStepper (USB one works perfectly for over 99% of people, however I don't think it's worth the risk of being in that sub 1% in order to save a few pounds), combined with a suitable PMDX BOB. PMDX produce some of the best BOBs, and have quite a few options depending on what you need to connect.
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As for wiring it in, if you can't find any guides/build logs here or over on cnczone, then I'm afraid you'll need to either figure it out yourself, or find somebody who can do it for you.
It would probably be worth taking some good photos of the existing boards and posting them up here, as others may recognise them and be able to help.