GM trucks titled prior to the mid-1950's were usually registered using the stamped engine number not the body digits pressed in the door ID plate. This practice has created many problems in later years as states became stricter in titling.
Unfortunately, many older vehicles outlast their engine and owners rarely rebuild the originals. To save time and certainly expense, a rebuilt unit or a used one from another vehicle would often be installed. This worked great until years later when state safety inspections began or the vehicle was sold out of state. With a prior engine transplant, there was no ID numbers that would match the title.
Even today, this problem occurs as older trucks with different engines are pulled out of barns and from the property line of a farmer's back field.
