The frame number will be on the left front outer side of the frame rail. This is just near the front bumper. The frame number is the serial number. If the other data plates from the dash are missing then the best way to get the correct date of manufacture is to write to Walter P Chrysler Museum to get the original build card. The build card will give you the correct info on the truck.
http://www.wpchryslermuseum.org/?id=390&mid=135
Also go the command-car .com
There is much great information there that will help. If you have any other question just email me.