Converting will expose you to many potential pitfalls, which, if you are aware of some ahead of time, might make the job less difficult.
"would a complete T5 tranny assembly from a fox body work"
Yes, it would. Please be aware of the considerable number of things needing to be addressed. First, clutch pedal assembly under the dash. Then, decision time, will you use a stock Mustang release system, or some other, maybe, hydraulic clutch release system. Next, do you wish it to function exactly like the factory '95 system? Speed control? Clutch pedal and brake pedal switches needed (you may already have the brake pedal switch). Computer. Stock is programmed differently with AOD from manual. Will work, but not as Ford wanted it to....(I've used both ways without grief).
Need new flywheel, clutch assembly, throw-out bearing assembly, input shaft pilot bearing placed in crankshaft. May need to modify floor pan for shift lever assembly.
There is a whole lot of sh!t to be addressed with this sort of conversion. I may have missed a few, like, driveshaft length. Are you SURE you want to attempt this? imp