First thing I would do is call Peter at South Bend clutch and ask his opinion.
Looking a your sig I would think a con fe would be plenty of clutch for your truck if driven on the street somewhat reasonably. How do you drive, what do use the truck for?
I can think of alot of reasons for what you describe, some are install related and some are failure related.
I'll put them in question form:
Was the flywheel resufaced when clutch was installed?
Was the input splines on the transmission clean not worn where the disk rides?
Did the clutch disc slide freely on the input shaft before install?
Was the bearing retainer OK where the throwout bearing rides?
Was the disc installed the correct way, ie, flat side toward flywheel?
Was to much grease used on throw bearing or input shaft thereby contaminating clutch?
Was throwout bearing arm and/or pivot ball worn?
Was the pilot bearing replaced?
Is the hydraulic master and slave working correctly?
Has a spring popped out of the clutch disc hub?
There is more but I'm tried of typing. Hope this gives you some ideas. Let us know what you find.