Here's a shot of the Nylon tunnel lines in a 74 911............
Your 70 and all 73 & earlier 911s should have steel lines and will pass the magnet test. If you are keeping the carbs, then the system is low pressure (3-5psi) and hose clamps will work fine.
If you ever plan to hot rod the car or put a late model motor in or upgrade to fuel injection, then you should use the High Pressure Polyamid lines with the correct crimp fittings.
Happy to help if needed.
Len