I have a 99 F-250, 6 speed. The truck had very low clutch pedal (pedal would have to be pushed all the way to the floor to disengage the transmission and as soon as the clutch pedal raised off the ground it would engage). So I tried replacing the hydraulic sys with ford pre-bled unit and I upgraded to South bend clutch, this helped a bit but it still wasn't good. What turned out to be wrong with the clutch is the pedal was bracket was wearing away!!! The bracket is made out of that "white metal" and the axle that the pedal rotates on is made of steel, while over the years that axle had worn through the bracket. It was 3/4" back on one side and 1" back on the other side, so the pedal was actually rotating about an 1' back from where it should have been.
Anyway I replaced the pedal and bracket ($180 from ford) and its perfect, its like a new truck. It also explained why i was always finding metal shaving on my Left foot