It'll go in. You did use the clutch alignment tool right? And when you tigthen the clutch down you need to be constatnly removing and re-installing the tool to make sure it slides right in with no tension on it at all. If you just tighten the clutch down with the tool in place but don't check on that, its probaly going to be bound up and that is causing your issues. Or its soemthing stupid like the wiring harness is falling in between the trans and bell whre you can't see it and boogering it up.
2000 Mustang GT Steeda #0048
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.