Transmission

Hi need some help here. I have. 2000 3.8L T5 manual transmission that either I have rebuilt or I found one it’s from a 1998 manual T5 Mustang. Will that fit in mine as well work I’m mine?
Yes it will "bolt up". No. It won't work as well.

The 1996-1998 model year uses a VSS contact style speed sensor. The VSS sensor is driven by a worm gear on the output shaft.

The 1999-2004 model year uses an OSS non-contact style speed sensor.

The output of a VSS sensor is NOT compatible to the signal type of an OSS sensor. The wiring is different. The type of sensor used needs to match what the PCM is expecting.

Here's is some more information that may help you to understand the difference between the VSS and OSS sensor.

T-45 Tail Shaft Swap

Try searching car-part.com for salvage yards in your area that may have units that will interchange without having to re-configure.