In NC, the law (I can look up the statute and post it if folks are that interested) states that the tag has to be visible for a distance that translates into its having to be lit... In the inspection procedure, there is a line to be checked off for the tag light...
However, in NC, you can run year of manufacture tags (the one with the year embosed in the corner back before we went to the stickers for updating tags) as long as the tag of registration is available for inspection. Most folks work under the assumption that the "hood number" stenciled on the tailgate equates to the YOM tag...
So, not many folks display their tags on MV's...
Also, in NC, vehicles over 25 years in age are excempt from inspection so the tag light needing to be checked off during the safety inspection becomes a moot point. (keep in mind that a larger vehicle such as a duece still is required to have an annual inspection as its weight puts it under the FMVCSA rules even though it is privately owned, but do your own FHWA periodic inspection...).
I used to run a tag on my M37 on a bracket that I mounted that had it hanging down from the rear crossmember (used a bracket with a light in it and fed it from a pigtail from the passenger taillight), but now don't. I had to pull it off every time I went offroading (the picktail had a plug so I could just pop it loose and then unscrew the bracket...). Mounting the tag on the tailgat presents a bit more of a challenge since you have to run a wire (if lit) that would be secure without interfearing with the tailgate operation and you want to avoid the pioneer tool rack...
I've seen some tags mounted to the bumperette...
If me, I'd see if the restrictions (if any) and having it registered as a historic vehicle worked for me and would go that route so I could be excempt using paragraph three of your laws as posted above.
Good luck.
