In that case, i feel there is nothing wrong with it. A lot of people clone the Road Warrior cars and i think it's just great. If YOU'RE happy with what you're driving and are getting enjoyment out of it, then that is the most important thing.
Now, in the case of a GTO or Chevelle SS or something like that, IF you're upfront about it and are doing it to capture the essence, the atmosphere of the car then i think that's fine too. If you're doing it to try to make big $$$, then not cool.