I knew those tops looked a lot like the treadle tops. I'm not terribly surprised that they are the same once the legs are removed. It is a good idea if you can find one cheap enough and have a set of irons that needs saved. The last treadle I bought the wood was in bad shape but the head and irons were ok so I bought it as a parts treadle. It would have been really easy to switch the irons to a new cabinet using your method.
Rodney