Ditto…LT1 has the disc installed backwards b/c pull type clutch. Also important to tighten pressure plate bolts to spec (I beleive 85 ft lbs). Take the two bolts off holding the slave cylinder. Have someone push on the clutch pedal while you are pushing the slave cylinder pushrod into the slave. It should have no trouble forcing itself out of the slave. If so, your hydraulics are good.
Did you say SPEC clutch or stock specification clutch?
SPEC is poop. I’m on my 2nd one & not happy. That being said, it should still engage/disengage.