I have one here said to be from a '40. The tailgate is 46 3/4". Next to it is my '47 pu and it's tailgate is 49 7/8" for comparison. I know ford widened for the '42 year.
If you don't have a tailgate they are available. Or were. They are not all that accurate from the factory...but they are. Held on with chains. Probably not a thought of mm.
