Your truck didn't come with a stud-mount paper-element air cleaner. It came with a clamp-mount oil-bath air cleaner. That's the only kind that will fit the carb on the truck. If the air cleaner didn't come with the truck, you'll need to scrounge around for a used one. It looks like this (the one pictured is on a Canadian-built truck, hence the decal):
If you want to convert to a passenger car style paper element air cleaner, you would need parts from a passenger car carburetor -- which parts you'd need would depend on whether you have the Carter or the Holley carburetor.
(where did you get the current carb?)