Sounds like you got maybe a hotter cam or an extra large Rochester QuadraJet (aka 'QuadraBog', lol) carburetor, those carbs were maligned by many, but the secondaries were so large that you could drop a golf ball through them, they would flow massive amounts of air and fuel at full throttle.
GM-Rochester manufactured some sweet gear way back then, my Uncle located an original '64 Rochester fuel injection setup for the small block Chevrolet, got it rebuilt and recalibrated and it went into a '64 Corvette and that was my first introduction to 'old school' fuel injection and the acceleration was positively Old Testament Terrifying, in my not-so-humble-opinion, had never felt anything like it before, or since.
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