Yes, if you refinish a car, it can still be considered an antique, as "antique" is more a statement of age than of condition or value. That being said, most collectors and avid vintage or antique car enthusiasts will say that the refurbishing or restoration must be stock, or authentic to the year, make and model of the vehicle.

Here in the United States, the Antique Automobile Club of America defines an "antique" as a car over 45 years of age. When you go to register your antique car or truck, however, you may find that can vary from state to state, as each has their own interpretation. The antique car era is generally thought of as from the beginning of the automobile up to the 1930s, and this is probably the best way to describe it, because as time goes on, the 45 year rule would begin to include vehicles which are really not "antiques". These automobiles are becoming harder and harder to find, as many did not survive the need for metals during WW1 and WW2. Because of this, those that you find that are in original or restored to stock can be very valuable. There are special clubs which exhibit and perform vintage cruises, in addition to those who simply collect and admire them. They are often sought after for parades and special events such as weddings.

Classic cars and muscle cars are from later eras and have a place of their own in American auto history. The same rules of restoration and refurbishing apply. Original, stock vehicles are almost always more valuable than those modified.

As time moves on, simply stating that a car over 25 years old is a "classic" is misleading. We probably have to come up with a new term for cars following the 1970's. After all, would you ever really consider the 1986 car you were driving to be a "classic"? ( A "classic" Honda Accord or minivan for example? )
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