The SON (Shipping Order Number) should be on the body tag attached to the driver's side inner fender. It was stamped onto the top of the radiator support along with the digits for the assembly plant and model year added to the beginning of the sequence. So, basically you would have the assembly plant, model year, scheduled built date and sequence number. The build record from Chrysler Historical would have both the VIN and the SON, tying both together,
The number would be covered by the sticker for the antifreeze but it can be viewed using a mirror to see the under side of the radiator support,
This only applies to American-built A body cars. Canadian-built cars had no SON attached to the car or the body tag.
Bill
Vancouver, BC