Pros and Cons of non-US spec,car as an investment

When I went to the LaJolla concours last week I saw a yellow Alfa Junior Zagato and the Calif, owner told me he had no trouble registering it because it had already been registered in another State. And he doesn't have trouble with mechanical parts because it uses the same 1600 as offered in the US models.

I would advise someone who wants a conversation piece to buy such a car--some model never formally made in U.S. spec like this car, the Renault Turbo II, etc,the Pininfarina Peugeot convertible, etc. except isn't there a downside in finding body parts and windshield o rside glass? On the plus side, I can envision these non-imported cars wouldn't depreciate when at any given time there would only be five or six for sale in the entire U.S.