Respectfully, recommend checking B-nut threads again because my C180H fuel-hose B-nut has 0.750-16 (inch) threads, requiring a 7/8-inch wrench on the B-nut, and the carburetor elbow looks like this:

It is a unique elbow in that it reduces 1/2-inch x 37-degree flare tube/hose to 1/4-inch NPT. Part number AN816-7J straight fitting (stainless steel, from Genuine Aircraft Hardware) is the only similar fitting I could find with respect to the threads, but it sufficed with custom hose from Aircraft Spruce.