How do I find out if the engine is numbers matching?

[elanmars]

I followed a link cody posted a while back that kinda decodes a vin and I was pleasantly surprised that my car came with a 400 (not a big stretch but it could have been a 318 or whatever).

So yes, how do I find out if it's a numbers matching engine? this would be REALLY helpful since I'm selling the car, it will give me more than enough in funds to get a '69 I found nearby and "finish" it up. I really wish I could just have both but I can't at this time.

Thanks!!

[1968Coronet500]

You can check the flat rectangular spot right obove the oil pan and the passenger side of the motor. It will match part of the Vin Number.