A quick look at Specification Manuals shows the door hinge pillar tag was the cab/truck ID at least into 1958.
Some states might have punched an ID onto the frame before Chevrolet did (people have posted that being the case in CA).
Do you have the engine ID?
Do you have the number of the original door hinge pillar ID plate?
Do you have the last title/registration (what code is on it)?
Good luck, Keith
