Fuel line fitting problem

[Isaiah92260]

So I got a new fuel line from truck shop and I have an issue.
The adapter I have already that goes into a nipple for a hose, isn’t the same size for the fuel line, neither is the hole for the carburetor. The brass fitting for the fuel line is too big.

I believe the thread size is 5/8 24 thread.(probably wrong)
And I believe the male adapter side that goes into the carb is 7/16 24.

AnywAys I went to auto zone, Orilleys, Napa and Home Depot and cant find the adapter. Does anyone know where I could find the adapter or the thread sizes?

I have a rebuilt Rochester b,