Standing Rigging
You might have to get new standing rigging since the deck dimensions are going to be different. I am not familiar with the O'days and I don't know how many shrouds you have for the O'day, but the C22 has the fore and back stays, the upper shrouds, and the forward and aft lower shrouds. Also, the C22 is a mast head sloop. Is the O'day also a mast head sloop, or a fractional rig. Ther boom on a C22 is quite high above the cockpit, and the luff slot is above where the gooseneck connects. Even if the O'day is a little different it should be ok. My opinion is that it could be doable as long as the sailplan does not get changed.