Matching numbers has more to do with whether your drivetrain is original to your car then anything else. If you look at your build sheet you should find your VIN number as well as a sequence number that will appear on your cars core support, fender tag, and engine block just below the left head. Build sheets are usually located under the rear seat ,behind a seat back, or on the top/rear of the glove box. The VIN number on your build sheet should match your cars VIN and the build sheets sequence number should match the core support and engine number. My 68 Dart is an early one but has the 2nd half of the VIN stamped on the top rear edge left side of the engine block with a corresponding one adjacent to it on the bellhousing. If all of these numbers agree with the numbers on the build sheet then you have a "matching numbers" car. Matching numbers cars are generally viewed as being more valuable because they have not been altered in their history. The rarity of the car plays a big part in whether "matching numbers" will dramatically increase the value of the car.