I thought they were 350-375? The origional posters didn't hit 375 with a cam, carb, and open headers. The stock one in the MM article, NON- blueprinted, made 281 with open exhaust off the manifolds. None of these were blueprinted from the factory, and were far from optimum. A carefully assembled one, with everything perfect? Sure, I can see more than the factory rating, but the average one I seriously doubt made much more. MM did a 383, and a 440 also, the 383 was very close, the 440 made a little less. I saw a trend in those builds, and that trend was that Mopar was pretty honest with their ratings. If stock 340's made 350-375 HP, they wouldn't have all run low 14's or high 13's.