Advice on a 625 CFM STREET DEMON CARBURETOR for 273 commando

625 is max effort with max velocity through the carb on a bench. Your 318 may not even pull the secondary air door past 50%. That would be a good GoPro video of a shot of the carb during a high speed pull ON THE STREET, (or a TPS wired to the air door to a dash gauge) with all its drag associated with a moving car. Remember the air-door style carbs only allow whats being demanded. not like a double-flusher (pumper) that is entirely linkage driven.