I took the the A series gasket to the bike wreckers to overlay with the bike heads. If it`s something you are wanting to do, take the CA gasket to Vic Motorcycle Wreckers. They are fairly helpful. Their prices aren`t cheap but they have good stock.
The CA is already DOHC, surely they dont flow too bad? I would think if you spent the money on a CA head that you would have to spend on a conversion, you would be miles ahead staying with the CA head.