When an american collectors car has the original engine, frame and gearbox. All stamped serial numers match.
Heard a Hemi Cuda was sold at Scottsdale for 1 million. But it was matching numbers.
In todays modern collector car world, cars are being sold as numbers matching when the original engine has been replaced with a correct part numbered, date correct block. Sometimes this even means the serial (VIN) number has been re-stamped to match...
When shopping for a classic be sure to ask if the drive train is original to the car. You will be surprised by the answers the seller comes up with to justify his car being matching numbers.