How to block off fuel return line in Classic Industries Fuel Sending Unit.

Hello Mopar experts,

I’m reinstalling a Classic Industries fuel sending unit with a 3/8 fuel line and a either 5/16” or 1/4” return line. I am running a carb and do not need the return line and therefore I would like to plug it. (See attached picture) I used a rubber vacuum plug as a temporary fix however I’m guessing that this is not the brightest idea. Any ideas as to what I should do?62E16CA1-F9EB-4E0D-8F21-EDF144DC2739.jpeg