Where is the speed governor located on a 1997 mustang?

A 1997 Mustang doesn't have a speed governor in the traditional sense of a mechanical device you can physically locate and adjust. Speed limiting on that model year is controlled electronically by the Powertrain Control Module (PCM), also known as the Engine Control Unit (ECU). There's no single component you can point to as "the speed governor." The PCM uses various sensor inputs (like vehicle speed sensor) to manage engine output and prevent exceeding a programmed speed limit. Any modification to the speed limit would involve reprogramming the PCM's software.