The tail light fits all passenger cars and sedan delivery for 1937-38. It also fits a few 1939 Chevrolets - only the coach and sedan cars (these are the models without trunks) and the sedan delivery. All other 1939 Chevy cars used a different shape tail light with a round lens.
For reference, the light in your picture is different from the one used in 1940-53 trucks only at the rear mounting face. The lump on the back has a provision for a mounting screw which was used in cars, while a flat back design was used for trucks.
I had been given these under the assumption that they would fit my truck…. There were small things that did not seem correct which is why I was asking.