I think you'll have no trouble registering it as "the model year it most closely resembles".
Shelby isn't listed as a manufacturer so a lot of us will go Ford Roadster for make and model. It's no problem, just bring your paperwork you have, read up on it ahead of time so there's no question on the day. I think you'll find you have an antique or custom built vehicle exempt from any emissions. You could even run blue dots if you wanted.
How to Register a Custom or Antique Vehicle in New Hampshire | DMV
The plates say Live Free or Die, your Arizona pals read that as Live Freeze then Die.