In 1940, GM began offering a slightly wider bed on their Chevrolet pickups. This width increased from about 46 3/8″ to 48 1/2″.
Of course, the tailgate also required a width change. For some reason GM added a much larger horizontal tailgate roll on the top and bottom. Possibly for added strength. This caused the two hinges to also change. They were now much larger in diameter than the 1939, but this resulted in a new problem! Heavy weight on an open tailgate caused the oversize hinges to bend and split.
In 1941, the tailgate roll and hinge was reduced in diameter, though still larger than the 1939 and earlier design. This new size hinge remained through 1953.
Solution to a problem: Pure 1940 tailgate hinges are not being reproduced. Even if you have a rare 1940 Chevrolet or GMC pickup with restorable original tailgate, your large hinges may be in very poor condition and not restorable. The solution is now on the market! A non-metal bushing is now available that fits over a 1941 hinge. This builds up the horizontal surface to equal that of a 1940.