Glenn,
First, welcome to WIX. I would tend to agree that the odds of this aircraft actually being BuNo 123557 are indeed slim given the narrative of it going "into the water" while operating off USS Midway. There were no heavy lift helicopters available and one would think that getting a ship alongside before it sank in order to lift it aboard is sketchy. You could order a copy of the accident report from Craig Fuller at
http://www.aviationarchaeology.com/ to discover whether the aircraft was recovered or was a total write-off.
Beyond that, perhaps either someone with specific knowledge of this aircraft or someone who knows where to locate the data plate will chime in. Then, it's just a matter of a tall ladder and gaining access inside. Simple, right?
Again, welcome aboard!