Ginter Books - Naval Fighters: Lockheed R60/R6V Constitution
The Lockheed R6V Constitution was a large, propeller-driven, double-decker transport aircraft developed in the 1940s by Lockheed as a long-range, high capacity transport and airliner for the U.S. Navy.
The first time I saw this aircraft was in a photo of a Bearcat and it was in the background.
This book covers this and more.