Is this an O'DAY 12, or a Widgeon? Same hull, different decks and rigs. Widgeon was built from 1963-89, O'DAY 12 from 1976-78.
If you have a Widgeon, I have a rigging diagram, plus 8 years of experience with rigging my own Widgeon. I also created an expanded version of the original O'DAY-Supplied Owners Manual and can print up a copy of that for you if you would like one ($10 printing charge unfortunately) . For the O'DAY 12, well..... I have many pictures and can offer help based on my years of general sailboat knowledge.
See pics below for ID.