Numbers Matching Question

[chevelle_ss_502]

Ok I am sure this answer is here someplace but I didnt have alot of luck finding it. A guy I know is selling a 69 Camaro and it is a SS car but doesnt have the original motor in it. It has a motor from another 69 Camaro but not the original motor from the factory. He is saying it is a numbers matching car. I always thought numers matching meant that it was the original motor with the vin number on the motor matching the vin number on the cowl or car vin number. And this is also true with the rear end and transmission. Am I wrong in what I am thinking?

Thanks,
Andy