Hi, I need help and hope there is somebody who really knows 400 engines. I am getting ready to sell my 70 GTO and no matter how much I research it, I can't figure out if the motor was actually built with the car or not. Here is what I have been able to find out: The Casting # is 7970071. The date, by the distributor is 09 with the last # an oversized O. The front date code (wich is the most confusing) 0273569 WT or WZ. I can't see the bottom of the Z (almost like a 7) The manifold dates K198 and K199 with a large 6 and 2 cast into it. With the car being for sale, I'd like to know what to tell perspective buyers about the motor. If anybody knows what I'm looking at, I'd appreciate it.