Is it the sticker on the air cleaner????

I am going to agree with the ideas brought forth by @DionR and @Dana67Dart and maybe add a few of my OPINIONS. Some engines are automatically HP. For example, the 340 (even the lower compression later models and the HEMI. To determine if an engine is HP, I think you need to 1. compare the engine in question to other engines of the same displacement, 2. What vehicle is it in, and 3. consider what else is going on that year. A 383 with a 2 barrel is not HP no matter how much good towing torque it has. A 383 with a 4 barrel in a station wagon or truck is not HP because it is there for working power, not performance. A 383 4 barrel in a Road Runner is HP because it was intended to provide a decent level of performance in a performance platform. If there is a 2.2 L turbo charged engine in a 88 dodge Diplomat, that is not HP. If that same engine is in an 88 Dodge Daytona with a 5 speed, spoiler package and performance suspension/tires, it is HP. If, as in 74, compression and power are down, an engine, like a 340, can still be HP if an effort was made by the manufacturer to squeeze out some decent power while following the rules.