E4OD swap time.
(SJ's ^ gunna love this one.
)
Actually, there's one good thing that comes out of a ZF -> E4OD swap -- it makes available a ZF and accompanying goodies for someone who will appreciate them.....
Sorry... back on topic, START with this simple "divide and conquer" test. Have an assistant work the pedal, full travel, while you slide under and measure the fork travel. At the very end of the fork, travel should be at least 1/2" to 9/16". If it's LESS, then the problem is "upstream" - hydraulics, pedal box / bushings, pushrod bushing, firewall (firewall shouldn't be a problem in that generation of truck, but still check). If you get at least the minimum travel, then the problem is "downstream" - fork, throwout bearing, pressure plate fingers.
But you may have two problems. If it's hard to engage and the pedal doesn't feel right, that's usu. a clutch disengagement issue (any of the above). The grinding, if it's grinding while going down the road NOT operating the clutch, then it's not a clutch problem. That would be low fluid, wrong/old fluid, or as said, rebuild time.