I pulled the gas tank to clean it out and see that there are 2 feed lines coming out of it. The PO converted to carbs, which I am sticking with. It looks like he blocked off a fuel line (that runs near the passenger side rocker). The other runs to the electric fuel pump. I would prefer to block off the (I'm assuming) unneeded fuel line at the tank, to minimize the risk of leaks.

Can anyone help me identify which line to block off at the tank and where to connect the other one to the car below the tank?

Look down inside the fuel tank where you will find a strainer (which should be replaced since you are already in there). This strainer has a pipe connected which is the fuel delivery, plug off the other.

Slight thread hi-jack, I have a 76 thats been converted to carbs long ago and the OEM feed line is still flexible, but while the engine's out, seems like a good time to update to SS feed line.
Question is the double rubber grommet at the firewall just behind the gas tank that leads the lines into the tunnel, I've traded to pull it loose with no luck and am afraid to destroy it getting it out. No way to pull the fuel lines with this grommet in place, so can it be removed without destroying it, and if so how ???

Thanks, easy enough. There are 2 connections on the car under the tank. Which one does the fuel delivery line connect to?

Re-read the part you quoted. The one with the strainer.

--DD

I was referring to the connection on the car, not the tank. But now that I look at it again, I see that the 2 lines are different size. That clears it up.

What is the other (smaller) line for?

Just to be absolutely sure of which is which, I would detach the fuel line at the carb and have someone blow or use compressed air at the fuel lines in the front of the car. It's hard to say what the previous owner did when they converted to carbs.

Our 914's came from the factory with fuel injection. I'm not sure what year/model car you have, but here's a simple diagram of how it functioned from the factory.
Click to view attachment

Barefoot, don't pull the grommet. 5/16" line will fit thru the holes just fine. Even with the bends.

https://www.youtube.com/watch?v=hxFRQTWLetw

Return. The fuel pressure regulator acts a little like a plug at the end of the high-pressure section. Think for a moment--if you have a hose with water running through it, and you put your thumb over the end, the pressure in the hose goes up.

The return line takes the excess fuel (that which sprays out around your thumb, in my analogy) and runs it back to the tank.

--DD