Underneath the fuel tankClick to view attachment

Sorry. Read the op wrong.

The wire harness connects to the fuel sending unit and the drain tube goes thru the hole under the gas tank. The other 2 are a fuel line and an evap line.

Do you mean on the second fuel line? There's a lot going on in this photo, so it's hard to know what you're talking about.

The car has both a feed and return line for the fuel system, but if you car was swapped to carbs at some point, then the return line isn't used and may explain why it's disconnected.

The wire and connector hanging is the fuel level sender connection, which plugs in on the top of the tank.

sorry, I realise now that I wasnt very clear
you have answered all the questions between you
The car is on carbs which explains why there isnt a pipe on the return

I think I'd be capping that return line.

easily done but why is it better to cap?

so I blocked it off but is wont run now so the tank will need to come back out to remove it to be sure that isnt the cause