I can only speak for 67 camaros, but i'm going to stick my neck out and say 68's also. I know all 67 SS cars had a 4 with a letter following, designating engine size & horespower rating. Mine for example says 4N on cowl tag, located on firewall. It's toward bottom of tag. Mine is a 325 H.P. 396 car. If it had said 4K, it would have been 375 H.P. 396 car. Small blocks had same type coding but can't remember letters on them. But they all had a 4 followed by a letter. I can't begin to tell you how many "SS" cars I've seen without those codes on tag. There are alot of fakes, or misrepresented cars out there. Some guys actually believing they have the real thing. I could go on with the stories but smashed my thumb at work today, and It's starting to throb typing. Hope 68 is same. See Ya.