fuel line/pump question

[por70]

I have a 1970 911T that now has a Weber carb set up in place
of the original, (zenith? mfi) I'm replacing the fuel pump and tank. The original pump has three lines, one supply to the carbs and two coming from from the tank, (bottom line on the tank has a
intank filter. supply I assume)

Is the other tank line (a return?) from the pump?
and.... do I need it for the Webbers?

The replacement fuel pump for Carb equipped cars only have
two lines, supply from the tank and the other goes out to the
Carbs. So........can I plug the second tank hole (upper) and
run just two lines..

Maybe even take out the intank filter and run an external filter
also?

Thanks for any help,

Bob