12 Valve fuel shut off

[brimc]

So I'm working out the details of replacing the electric fuel shut off solenoid on my p pump 12 valve that I'm doing in my 86 Silverado. I want to be rid of electrics, electronics, wiring and automotive computer nonsense as much as possible on this build. So I want to install a simple push/pull cable to manually open and close the shutoff valve. I have searched and seen a few different types and styles and think I have a plan other than I have two questions that I am not sure about and I thought maybe some of you would share your thoughts.
First, when the engine is off, not running, does it matter what position the shutoff valve/lever is in? Second, does the cable have to be "locked" or maybe spring loaded to hold either the on or off positions?