My friend had a 1987 GT he bought new. When we replaced the clutch, we did TOB, flywheel, disc, pivot stud, pivot arm, clutch cable and quadrant. All Ford Motorsport items. T5-Z also installed. The clutch was a stiffer unit, and after a few weeks the clutch acted like your clutch does. The clutch pedal lever under the dash broke where it was welded around the round bar. When it was replaced, the new Ford part was an updated piece with more metal around the clutch pedal assy. We never thought about that item coming apart, but the heavier pedal and high mileage (188,000 miles, highway car) the factory item failed. After replacement everything worked as normal. The factory update was made around 1989/1990. It may not be your problem but keep this in mind when putting a HD clutch in a FOX body.