The vehicle ID plate in the door jam will identify when and where the cab originated, along with the body style. Counting the number of springs will usually tell you the load limit, too. On the original engine, there should be a number stamped into the raised area next to the distributor. This is what most states used back then used for the VIN number. It will also tell you the year of manufacture and cubic inch displacement of the engine. What looks like a seam in the running board may well be a rust streak from where the stake pocket drains down. What looks like frame sticking out may be a custom hitch or step bumper. Better pictures will show if it is indeed frame, or merely bolted to the frame.
