What about the VIN in the cab?
I need to get one.
For legal reasons I don't think they would sell you a VIN plate on its own, but I've bought whole dashes with the VIN still attached and they didn't seem to care. Just drill out the rivets holding the VIN on, and slip it into your pocket or the bottom of your tool box.
Make sure you run a history check on the VIN before attempting to register the vehicle under that number. I don't know if PnP reports all of the VINs of incoming vehicles as offically scrapped, but there could be other nasty surprises in the donor vehicle's history.
Unless you meant swapping your existing VIN into a replacement cab... in which case I see no problems.