* Specific Engine Code: GM used various internal components (camshaft, carburetor, etc.) in their 454s for different applications. An RV engine was likely tuned for low-end torque rather than high horsepower. You'd need the engine code (usually cast into the block) to get a more precise idea of the original factory rating. Even then, factory ratings are often optimistic.
* Condition: A 50-year-old engine's condition significantly impacts its power output. Wear and tear on pistons, rings, valves, and the overall engine health will affect performance.
* Headers: Adding headers *increases* horsepower and torque, but by how much depends on the header design and the rest of the engine's setup (exhaust system, etc.). Headers primarily improve exhaust flow, leading to better breathing for the engine. They might add 10-30 horsepower, depending on many variables.
* Carburetion and other modifications: Modifications to the carburetor, intake manifold, camshaft, ignition system, etc., all dramatically affect horsepower and torque. An RV engine might have been modified by a previous owner.
In short: A stock 1973 454 from an RV likely produced somewhere in the range of 250-300 horsepower and 400-450 lb-ft of torque *at the crank*. With headers, you could expect a modest increase, perhaps to 280-330 hp and 420-470 lb-ft of torque, but this is just a rough estimate. Without knowing the engine code and its condition, a more precise estimate is impossible. A dynamometer test would be needed for an accurate measurement of the *actual* horsepower and torque after installing headers.
