englishkid,
Are there any leaks on your garage floor?
I had the same thing recently in my '67 and noticed a discoloration on the garage floor that made me investigate further.
My problem turned out to be the rubber fuel line in the middle of the car. From what I have read/seen Porsche put a rubber fuel line in the mid section of the car to join the two metal lines to accommodate for body flex. Of course with age its going to crack and leak.
Get underneath the mid section of the car (unless you are made of paper or have a pit you will need to jack the car up - please make sure you take all the safety precautions required) with a torch and take a look at the line. You should see something like this:
I recommend using a torch because the first time I looked at the line I didnt have the torch and couldnt see how bad it really was.
It is also worth checking all your other lines.
I have also been told that the fuel smell may just occur if the o-ring on the fuel cap has past its use by date. It is worth checking this too (a new o-ring is a few dollars).
Best of luck