Steve,
Chevrolet did not put any ID codes on truck frames during the Advance-Design years (1947 through 1955-1st series). However, some people have reported that they have found a number stamped on the frame - this was done sometime after the truck left the factory. CA is one state that some people have reported did this - it is not clear if this was done when the truck was first title/registered or if this was done at some later time in the truck's life (by the original dealer or by the State Police).
As Bill stated above, there is a Vehicle Number (sometimes called a Vehicle ID) that is located on the driver's side hinge-post. There is also an Engine Number pressed into the pad/ledge just to the rear of where the distributor enters the block.
The use of the Engine Number is problematic because the engines in these old truck were most likely been changed over the years.
I had a 1948 Panel Truck that was first bought/titled in VA using the engine number. I have a 1954 Suburban that was first bought/titled in VA using the door-post VID. VA and most states have no on-line title-records for vehicles older than 1972.
Tim
