Curiouser and curiouser... As Tim's link details, the Vehicle Serial Number for a 1950 1/2-ton starts with 1 or 2 numerals that identify the assembly plant, then H for 1950, then P for 1/2-ton, then a letter for the month of assembly, followed by the sequence number. That's the number that was originally on the door plate. Since your door plate number does not fit this pattern, it cannot be the original plate. Despite the way the numbers are stamped - not always straight or level - the factory was always concerned about the serial numbers.
There is much discussion about the fact that some states used the engine serial number as the VIN on the title. I have read that some states removed the body serial number tags... though that info needs a good citation.
If your title has as the VIN a number that agrees with the number on the door plate - no worries. If your title has as the VIN the engine serial number of the actual engine in the truck - no worries. Any other mismatched numbers - you do have worries... Though most states have a legal way to overcome those types of title/VIN problems, but you may have many hurdles to jump over.
