David's description is the closest. It is on the firewall, not behind the kickpanel. It is a few inches from the corner, basically where the firewall becomes vertical above the rug.
There is a red button on all Ford fuel pump shut off switches. It is always on top, because it is actually on top of a cylinder which has a moving piece inside. When a hard impact causes the internal part to dislodge outward and up, the red top button is moved upward. Resetting it, pushing down, resets the internal piece, which connects the power.
It's a great switch that could be used as an anti-theft device. You could use it as a hidden switch to disable the any vehicle circuit. Regards,