Fuel leaking around large brass plug (fuel inlet valve?)

[zuburg]

I finally got my 1956 T-bird to start on a newly rebuilt engine after a 5 year saga of replacing tons of mechanicals (engine, Fordomatic, front suspension, brakes, etc.)

Now I have fuel leaking around a large brass plug at the rear of the carb. I think it might be above the fuel inlet valve. There is a rust colored gasket under it. This carb was rebuilt using a comprehensive rebuild kit several years ago but just now being used for the first time. I assume I should buy a new gasket, and or plug? Or could I use some kind of thread sealer to fix it?

Here are some pictures that show the plug on the carb and laying on the bench for identification purposes.