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

73Dart340Sport said
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?View attachment 1715512411

The rubber cap like in your picture has been on mine for years with a hose clamp. Probably not the best solution, but it works. Replaced the fuel sender recently, it was still in good shape, so I put it back on.