This was a Mustang Mk.Ia diverted to the AAF. Some Mk.1a types were eventually converted to tactical reconnaissance or F-6As.
Some were accepted by the AAF as P-51s, others as P-51-1 and two as P-51-2. Two were later converted to XP-51Bs/XP-78 (S/Ns 41-37350 and 41-37421).
My regards,
Widewing