My dad had a 1956 Bel Air with the factory power pack (4bbl carb & dual exhausts). That little Chevy was QUCK!
It started clacking on one of our vacation trips, and he bought a 1959 Impala with the 348 and Turboglide in Yukon, OK. It was a POS. The clacking noise turned out to be from an extra screw in the carb that had been there from 1956 to 1959. It sold before he completed signing the papers for the 1959.