I just sold a very origanal 69 Coronet 500, 383HP auto with A/C. It is a numbers matching car, the engine is turquos, and is stamped HP. From what I have found is that the A/C and non A/C engines have the same cam, just a differant distributors, something about the advance curve. A simple look through a factory parts book shows (1) cam number for HP engines, and lots of choices for carbs, and distributors. I have a friend who bought a 70 Challenger 383hp A/C new and still has it. It always has been a dog, I talked him into changing the distributor and wow!! the car is alive and has never run stronger.