In my opinion the 3650 is the most reliable easy to quick shift transmission i have ever used in any mustang pre 2014. I spent about $900 on new parts to rebuild it when I first built the car just as preventative maint but there was technically nothing wrong with it even though it had 110k mi on the car. Making sure the clutch is adjusted right it also critical. Need to make sure when clutch pedal is all the way down that it doesn’t try to lurch when putting into gear at a stand still.

Also i have always used the steeda triax shifter cause it has overshift stops that are adjustable.