Russell,
I don't think they are new manufactured engines. When Herkimer-OK shut down many years ago, there were a few cubic miles of spare parts left. I think all the Cub 1/2As we're seeing are assembled out of those parts.
Power? Not bad by 1952 standards. Not real bad today, against ordinary reed valve Cox engines. The Cubs might even be a bit faster than a typicall Babe Bee.
A guy who goes as DesignMan on other sites knows a lot more about both. If he shows up in here, hit him for more detail?