318 Cam

Gross horsepower was just that, the total amount of horsepower the engine made when the factory rated it. SAE net horsepower is a uniform standard which simulates the engine as installed. That means with the air filter on, fan belt on turning the water pump and alternator, and the complete vehicle exhaust system. Also the measurements are taken at or corrected to a "Standard Day" (15 degrees C, seal level, and 29.92" Hg). Before 1972, manufacturers could pretty much rate an engine at whatever they wanted to.

If you are running a 15 second quarter with 2.76 gears, I would WAG about 250 hp as is, not knowing your actual weight. If it were me, I would go looking for some 3.23 or 3.55 gears about next. That should be some pretty good bang for your buck.