Everyone assumes that prior to 1968 there weren’t any numbers matching cars made. Seems like many people think numbers matching includes the engine and transmission. In actuality 1967 had numbers stamped on the rear cross brace, rad support and fender tag. These numbers were matching, so in essence that is a numbers matching car. All the rest were accessories/add ons. Something to think about on a cold winters day.
And... they are the important matching numbers. Unlike a GM car made before 1972, the VIN stated what engine the car came with.
There are no "numbers" like VIN's but there are dated parts, engine and transmission numbers. You can't just dump a 68 383 in a 66 and it's the original engine. My 66 original block is cracked. If I wanted to lie I'd have to get a block cast close to cracked one. That's not all engine assembly date comes into play that needs to close to original date also. Have a block cast 2 days after my original but the engine assembly date is 3 weeks after my car's scheduled production date.