We are not sure how far manufacture of the two prototypes had proceeded by the time it was cancelled. Certainly, nothing solid remains today other than the 1944 wind-tunnel model which is now displayed at Woodley. It is well worth seeing as an engineering tour-de-force because of the accuracy in the fashioning of the wings (as we found out when digitising it a few years ago). Certainly, there is no trace of any of the drawings in the UK, nor in the archives I and others have searched in the USA. But it is possible they are in the Bell archive, now privately owned and, I believe, inaccessible.
The all-moving tail is a difficult one. I believe compressibility problems with the P.38 in the late 30's made Lockheed fit fully-moving tailplanes. The requirement for them for the M.52 seems to have originated from Farnborough. But I might have got that wrong.