It appears that "Toddster's" problem was solved so my comments might be a little late. In any case I will post some of my knowledge pertaining to the registration of trucks, especially older pickups in several states.
The main requirement that most states want on the paper work for a commercially rated vehicle is the unlaiden (empty weight)... The unaiden weight is usually printed onto the registration card when the truck is first sold. In many states, 1/2 tons from the 1930'/40's are exempt from this requirement because the original manufacture did not rate their light pickups.
With the exception of California, in the past, many of the states required that you pay fees based on what the maximum GVW was going to be. Therefore, if a truck has/had 5000 lb's painted on the truck, that was the maximum GVW of the vehicle.
I have to agree with the earlier comments on this thread that someone in the local DMV had no idea what the requirements for licensing the vehicle was.