Used to be that people would refer to an antique car or truck as one that was at least 45 years old. A classic was 25-45 years old. The problem is that as time goes by, these don't mean the same thing. Can you imagine a 1986 Honda being considered a "classic"? How about your 1985 minivan! Is your classic 1956 now an antique?
I prefer to use consistent references to a span of specific years. For antiques, I would consider anything from the invention of the automobile through the 1930's to be "antique". The "classics" would cover cars and trucks of the 1940's through the 1960's. Muscle cars seemed to dominate the 1960's through 1970's. Mixed in there you have your street rods, hot rods, rat rods etc., but these terms seem to address more of how these vehicles are used. For instance, you can have a 1930's rat rod, or a 1940 street rod...or just as easy the opposite. You can hot rod just about anything if you're referring to beefing up performance and power.
At Motorheads Performance, we specialize in vehicles from the 1920's through the 1970's. We see a variety of cars and trucks, and love the fact that our customers are so enthusiastic about their rides. I, for one, feel we need new terms for vehicles of the 1980's and 1990's. Many in this range are now over 25 years old, and it's just my opinion that it'd be a shame to lump these in with other true "classics"!