Though items were shared between GMC and Chevrolet trucks between 1936 and 1946, General Motors made sure many parts remained very different. The GMC dealers preferred very few things to be similar to Chevrolet. Their customers needed to see an almost stand-alone truck with the higher price they were paying.
One very obvious difference is the change in tail lights. There is no comparison. The massive GMC stamped one piece steel bracket combined with a redesigned 5-inch tail light makes the pair a “one-of-a-kind”. They do not interchange with Chevrolet during those year.
It was not until the new body style in mid 1947 that the two brands shared tail lights. When the larger GMC’s 5-inch light was discontinued on trucks in 1947, Chevrolet introduced it on their 1949 through 1952 station wagons and early GMC buses. It was placed in the center of the gate and was the only factory light on the vehicle.
Even though 1936-1946 taillight was used for so many years, it is becoming very difficult to find. Most GMC pickup restorers use the reproduced Chevrolet rectangular design and only a few GMC perfectionists are aware that there is a difference.
A shop in the US is attempting to remake this bracket; however, if this happens the tail light will be almost as big of a project to find. It is not being reproduced.
The photo below shows the real GMC tail light and bracket of the early years 1936-46 GMC.