Personally I think the so called twin P-40 is a hoax
Probably some Curtiss staff - personal built, what ever it was, just for fun. They then added a former P-40 serial to the fin, just to make it look more "real"
Looking at it, it really looks crappy to me and I doubt anyone would have wanted to fly a contraption like that.
Unfortunately Aviation Archeology is down again, so I cannot check their present details, but the real P-40C 41-13456 had a accident on 18 Feb 1943 at Craig Field. I don't know exactly what LACGL stands for, but some kind of landing accident no doubt.
Checking if anything else happened at Craig Field that day, I notice that an AT-6B 41-17179 had exactly the same kind of accident (LACGL) that day on that same field. Hardly a co-incident!
No way that the USAAF had the real P-40C bailed back to Curtiss to have "fun" with and later convert it back to a standard P-40C again. If you want me to believe that, I certainly need more data than any site gives.
Cheers
Stig