Need help bad!!!

Keep an eye on your fluid levels.
See if anything is bleeding.
But sounds like you've pretty much ruled that out if all has gone well.

What do you mean by replaced the whole clutch assembly?
If it feels strong as per usual engagement feel then there's a good chance it is engaging correctly.
Pressure plate pushing back through good hydraulics giving you a good pedal feel.
But your bum is telling you that the clutch itself isn't "biting/engaging/gripping"?

But it may depend on what's left to engage.
You say barely engaging, does that mean "barely gripping"?
Did it usually start engaging off the floor or is that new?
aka where does it usually start engaging, what does your bum tell you, what does your foot tell you.

If you don't know what your bum tells you then this has been a strange post.

Oh and did you do anything to the truck prior to this happening.

Open the bleeder then press the pedal down. Bleeding a clutch is not like doing brakes. I suggest using your hand to slowly let the pedal down and when its on the floor tighten the bleeder screw and lift the pedal back off the floor. That is the correct way to bleed it.

have you had the clutch out? disc could be worn down, how many miles the truck? may be time for a new clutch disc or possibly an entire clutch kit

Not to sound silly but,the two hydraulic lines upper and lower could be collapsing internally.This reduces fluid flow and makes pushing the pedal in and out seem weak.I would humor yourself and buy a new upper and lower hydraulic line and then rebleed.The outside might look good,but inside under pressure it might be reducing the flow of fluid and possibly create the problem.Since you did a full clutch kit(aka pilot brg,throw out etc) rules those out to me.Unless your pedal adjustment is way off in the cab(doubt it) things that came to mind tired as I am tonight.The idea above is plausible and thought the idea might be good to suggest.

Not totally highjacking but, My 89 B2200 been working flawsly until a stop at a drivethru. Turned motor off tranny in netural. Went to leave and I could not shift into gear. Turned motor off tranny shifted fine in all gears. Shifted into first with motor off and started truck and away I went with clutch depressed. Nursed it home and bought Clutch Master & Slave Cylinder and still the same. What Up?

Rockin - have someone repeatly push in the clutch pedal as you watch to see if the slave cylinder is pushing the clutch release lever on the transmission as it should. That should help isolate whether the issue is with the hydraulics or inside the transmission bell housing.

I'm assuming that you bench-bled the clutch master cylinder and then after installation bled the clutch system properly.

Did you ever figgure this out? Mine is doing the same. Replaced the slave about 4 months ago and now I'm going to replace the master. The clutch engages about 1/2" off the floor. Not really sure why.

Replace the clutch master; bench bleed it first. Then bleed out all the old fluid in the hydraulic system through the clutch bleed screw. These trucks have weak spot in their clutch hydraulics.

Aleays change m/c and slave at the same time.