Fuel level sender with return line?

Gas gauge is wildly inaccurate, so I probably have to replace the sender.

Autozone asked it I want it with or without return line.
I would not have expected an El Camino to have a return line in '68.

I'm thinking I do want the return line, so that I can put on my Edelbrock Pro-Flow injection later.
I can just block off the return port until it is needed?

I don't seem to have good luck with Q-Jets, this one tends to have a gas smell, and is flat on power at top end.

400 small block.