I would not suggest trying to convert a 1972-78 O'DAY 22 from Keel to Keel/CB. Is it impossible? NO! Is it practical? Not really! The 22 keel is molded fiberglass with lead ballast glassed inside, so you would need to somehow cut a slot in the keel/ballast combination (and thereby reduce the weight of the ballast, weight that would need to be added back) which would be messy at best. Then glass in some form of CB trunk to house the CB, after building a CB. If done at the factory while the boat was being built, or better yet using a bare hull bought from the factory...it might have been an interesting experiment!
I used to own an O'DAY Widgeon (12') and sailed her a lot, I felt that I became very skilled at getting the most out of her using the original (and 20 year-old) sails. I once had a 22 out point me and sail by.......well ,that did it! I ordered a new mainsail soon after (should have replaced jib too). The 22 is not going to outpoint a J-22 or any "racing" design, she was not built for that although a few 22 owners have done OK in racing. With sails in good condition, a properly tuned rig (based on the owner's manual, you don't need to tune her like a racer!), and a skilled skipper, the 22 will sail as well as any similar boat. Remember, the 22 is a typical 1970's trailerable sailboat, ease of trailering and stepping/unstepping the mast were high on hte list of design parameters I'm sure! Were I designing the 22, I'd have given her a taller mast and a K/CB from the start.....but O'DAY introduced a darn good compromise boat in 1972 and I'm sure that keeping the price reasonable was also important...thus the short mast and shallow, fixed keel. I guess that by 1979 the added cost of building the boat as a K/CB design could be justified and starting in 1980 the taller sailplan came out. Perhaps as a lead-in to the 222??
I would think that an early 22 will sail just fine as she is, maybe pointing 50-60 deg off the wind instead of a raceboat's 40-45 deg pointing ability....but she will point OK. Many 22 owners have switched to an overlapping Genoa instead of the working jib (most also added a furler with the genoa) and this might help compensate for the fairly small mainsail of the masthead-rig 22. The 22 also needs to be sailed "flat" ie: with little heeling to maximize the bite of the shallow keel, one possibility that might help (and would be less costly and labor-intensive than adding a CB) is to make the keel deeper by laminating an extension below the keel (glass over wood or foam, maybe some kind of ballast as well to stiffen the boat?). Yes ,it would mean deeper draft and mean it will be harder to float the boat on/off a trailer......but it is an idea.
BTW, Joe.. I enjoy seeing all the pictures of your boat! It is becoming a great reference just in case I ever do move up to a 222 (or at least a 192?). I need to start looking at all the pics I have of my DS II........maybe post a few?