Let's indulge this idea a moment...
A finned heat sink is bidirectional. So, if you were to blow hot air across the fins, you would raise the temperature of the zenith carb bowl. If you blow cool air across the fins, you lower the temp. What defines the air temp is the reference of the carb bowl temp. So, you have to have air cooler than the carb bowl moving across the fins to make this work.
On my Model A, I do not feel any air from the fan blowing across the zenith carb. The fan is above the zenith. The only moving air it would receive is when the car is in motion. I suspect the air moving through the fins with the car in motion will have come through the radiator already, taking with it the heat from the radiator fins as it removes heat from the coolant via the radiator.
I'm not sure there would be a major advantage here. Especially when the car is stopped at a red light or parked on a hot day. I think your best bet would be to cool the fuel entering the carb. Perhaps a coil of copper fuel tubing that passes through a super coolant fluid before reaching the zenith carb bowl. Example- coil of copper tubing inside a coffee can full of ice water. Though, I would suggest you opt for a super cooled fluid mmore robust than simple H2O in its sub-zero state, which is very temporary.