A wooden crate would be best way to ship. I have had several NOS parts shipped from east coast to west coast in wooden crates with no problems. 2x4 sides with 1/4 inch plywood sides and some filler to keep the tailgate from bouncing around inside will do it.
Yes, it will add to the coast but the buyer (hopefully me
would pay for materials and shipping costs.
Let us know when you decide. Looks like you have 2 if not 3 people interested. I've been looking for a NOS tailgate for a while, this would be awesome!
Cheers