Well it is definately a 46-47.1. These trucks didn't come with a vin number per-sey. The number stamped into your ID plate will give you the information you seek. I don't have my chevy decoder book(the chevy restoration manual) with me right now so I'm not much help with that.
One thing you do want to do is keep track of those screws that hold on that ID plate. Those are the only ones like it on your truck and are just for the ID plate. You can get a repro plate and stamp your numbers in it.
Check the links for the restoration manual from Chevrolet. It's free!
Good luck
George
