After a certain year too, the driver's side door opening had a decal with the VIN identifier on it. Top of rear panel, above the striker plate.
I think it started showing up in about '69 without the VIN, then in late '70 or so, the VIN was printed on it as well.
I could have the timeline wrong, but either way, I guess that at some point they figured that something more permanent than a glovebox door tag was in order.
However, these decals deteriorate, get painted over and lost when doing body work, but that doesn't seem to deter many DMV's from registering the vehicles, so like Kyle say, the glovebox door is your friend.
If they get a little sticklish about things there in GA though, you might find they want to verify with the frame numbers. Heard of it happening, so worth noting.
With luck, you'll find a good glovebox door from the frame donor.
Paul