The Holley 600 CFM is a popular choice for performance builds. It is a double-pumper carburetor that provides excellent fuel delivery and throttle response. The Edelbrock 600 CFM is another good choice for performance builds. It is a single-feed carburetor that offers good fuel economy and throttle response. The Ford Motorcraft 4300 Autolite 2-barrel is a good choice for stock or mildly modified builds. It is a reliable and economical carburetor that provides good fuel economy and throttle response.
Ultimately, the best carburetor for a 1971 302 engine depends on the specific needs and goals of the owner.