* Gross horsepower: Manufacturers' advertised horsepower figures from this era were often "gross" horsepower, meaning they were measured without things like emission control devices and other accessories that would reduce power in real-world driving. The gross horsepower for the 1975 454 in a C10 was typically 270 hp.
* Net horsepower: More realistic is the "net" horsepower rating, which reflects the power actually delivered to the wheels after considering all accessories and emissions equipment. The net horsepower for a 1975 454 in a C10 was likely closer to 180-200 hp.
Without knowing the exact options on a particular truck, it's impossible to state the exact horsepower. However, the range of 180-200 net horsepower is a safer estimate for real-world performance.
