I’m not aware of 2bbl dual snorkel air cleaners existing but then you can fill a warehouse full of stuff I don’t know.
Check out this website for more info:
Nick's Garage - Air Cleaner Identification
Perhaps your 318 has been upgraded to a 4bbl already? The opening at the base of the air cleaner is larger on a 4bbl so it’s not ‘easy’ to just rest a 4bbl cleaner on top of a 2bbl carb.