Imprimartin:
I talked to TAN books and they said that they were so old that the statute of limitations has run out and so it is fair game.
I suggest that you talk to someone knowledgeable about copyright law before you take on this task. Does the Radio Replies Press Society still retain a valid copyright to this work? You need to find this out, and you need to get written permission to create this CD from TAN Press that would stand up in court.
TAN Press could subcontract you to create the CD. You could get a royalty commission from each CD sold. That would be a win-win situation for TAN Press and yourself. If you would be willing to work for compensation by commission, TAN Press would have no up front costs involved, and they would get a product to sell. Heck, this could turn into a career. TAN Press has a lot of works that could use this treatment.
I would buy a CD of Radio Replies that is indexed and hyperlinked.
Scanners and OCR software are improving all the time. High resolution scanners are cheap now, but they require a fast processor in a computer loaded with enough RAM to use the high resolution data, since the scanned document is a bit mapped image that needs to be converted by the OCR software.
If you buy some used copies of the books that you want to scan, you can cut the pages out of the books so that the page to be scanned lies flat on the scanner. It has been my experience that helps a lot to get scans that the OCR software can convert efficiently.
You will still have to proof read word for word the OCR generated text against the original text. Puntuation and mispellings errors inevitably will occur in the OCR conversion process. Different OCR programs will work better or worse for any given page layout and typefont. One particular OCR software might work best for the layout and fonts used in the Radio Replies book.
You could contact New Advent and ask them what they learned by scanning in the Catholic Encycopedia. That Encyclopedia used a very small font for the footnotes, and that project began when scanners and OCR software were not as good as what is availble today.