Help with checking numbers

On my own car! I am not a numbers kind of guy, but was told when I purchased this '72 Duster 340 that the engine and trans were supposed to be the originals. I would like to try and verify that for what its worth. Not sure what numbers are stamped on the block and trans that tie back to the VIN? In 72 would those numbers be the same as the complete VIN or possibly only the last several digits?

Thanks,