Phantom Fuel Leak 911sc 3.0l

[CROWSC]

I have a 1979 911 SC, with a 3.0L. I am in the middle of restoring the car.
I started the car a couple of weeks ago, and smelled fuel, I pulled it out of the garage and saw a small puddle of fuel on the garage floor. I shut the engine down and pushed the car back into the garage and figured that I would deal with it later. About a week later I turned the ignition on without starting the car and looked underneath and the fuel was dripping out at a fairly good rate.
I started searching with a flashlight and mirror around the rear of the engine and couldn't find anything. I pulled the blower motor and air cleaner filter housing to gain better access. Then searched again. Could not find anything. I turned the ignition switch on again and let the pump run and searched the back of the engine as well as I could, and the fuel leak was gone. No more fuel leak at all, and no fuel smell. Now I am really freaked out. I started the car and pulled it out onto the driveway and let it run for about fifteen minutes and kept looking for the fuel leak, and the leak is gone.
Anyone have any ideas of what the heck is going on?
Appreciate any help.

[David]

The stock fuel lines on a '79 are pretty much toast by now. My bet is it's the pressure/supply fuel line through the tunnel that's leaking between the fuel pump and tunnel or between the tunnel and the engine.