The thread that Geoff linked to was a Granada conversion that came through my shop that the owner was having problems with- mainly the fact that he could not turn the wheel fully. I don't like that conversion due to the reasons stated.
Look up Toms Classic disc brake conversion on ebay. There are also one or two conversations about these kits in this forum. I installed a kit on mine and, in spite of a hiccup or two that Tom had been good at responding to, I'm satisfied with the result. The kit uses rotors and calipers from an S10, so replacement parts are cheap and readily available anywhere. In fact I can upgrade to Wildwood performance if I so choose in the future.
The key to Tom's kits is that he uses the factory spindle and uses special bushings to convert to late model rotors. Then he builds a special bracket to carry the compatible caliper. In my case the GM caliper has to be machined in one small location- a 'rough' operation that can be done with simple tools.