new guy with a question

[butler57]

I'm very new to the site and thought I should introduce myself. I picked up a '72 earlier this summer and found this site to be an excellent source of info. One of the first things I did on the truck was pull out the dash cluster and fix the gauges and lights as the only thing working was the speedo. I tracked down everything posted on how to tell if the gauge was working and ended up only needing to replace the float on the sending unit. Anyway, I really appreciate all of the knowledge that is shared here. Sure helps out.
here's a picture of the top of the gas tank. Any idea why the PO would block one line?