no engine info

At one time I had a 1968 dart GTS. If I remember correctly it had an engine code of "O". Which denoted "special order option". The car was a 383/ 4sp/ 8.75 We checked the numbers on the engine, and it was a Police 383. Now I could be wrong about some of this, as it was back in the mid to late 1970's, and I am going by memory, and at the time I was not into Mopars.