1992 should be a cable driven speedo. You wasted your money on the speed sensor it's just used for ABS and maybe cruise control. Changing speedo gears isn't going to make it work unless the teeth are stripped, just change the reported speed relative to transmission shaft speed. Could make it not work though if it isn't the right gear to mesh up with the drive gear in the transmission.
Since you replaced the cable and tested the speedo, your driven gear in the transmission is probably gone.
Did the odometer still turn when driving, or did both quit working?
FWIW my 68 F-100 doesn't have a working speedo either, that odometer does work though. Cable and gears work even if inaccurate, just speedo stuck/broke. Rather than fixing I picked up a cheap GPS HUD on Amazon and keep it on the dash. Eventually I'll fix it, but probably going to upgrade whole cluster to Dakota Digital.