I haven't had the Fair '39 or '40 out in a while, but I believe they are both blank on the inside covers. World's Finest were blank on the inside covers until about #8 or #9. My #11 has a Table of Contents on the inside FC and a house ad for the Big 8 of DC comics on the inside BC (Action, Detective, More Fun, Sensation, All American, Star Spangled, Adventure, and Flash).
Also, I hate to disagree with MrBedrock, but my Big All Americans have paper covers, not cardboard. They also have all blue printing on the inside covers.