I ordered a fuel sending unit with a "guaranteed fit" for my 69. The problem is the one the sent has two tubes and the one that's in there only has 1. Can I still use it and cap off one of them. The gas tank already has a vent on the side. Below is a picture of the one they sent.

 

Yes you can cap the return line.

 

Thanks. Dumb question, what can I use to cap it?