f body people, my clutch is squeaking, whats wrong?

if it fits and that is the one they gave you use it then. Past few builds ive ran a pilot bearing not a bushing.

assuming the trans was level when you filled it you should be good there.

when you last removed trans did you inspect the input shaft for unusual wear? did you try to spin the shaft to feel for anything? also when you checked the fluid did you notice any metalic to it?