Ford F150 - Inertia Switch

Does anyone have an idea where the inertia switch for a 1991 f150 4x4 would? My girlfriend will be withholding favors soon if I don't get her truck running. Thanks

Either on the firewall in front of the brake pedal below the steering column, or on the firewall just R of the hump at the front of the passenger footwell, or on the R A-pillar behind the kick panel just below the glove box. It should be the newer style with a red button.

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