Sounds like the pilot bushing. Did you replace it when 'everything' was gone through? The answer should be 'yes.' And, did you verify the ID and OD? Answer should also be 'yes.'
I had the exact same symptom with my Mustang years ago when I put a new clutch and pressure plate in it. Turned out that the 'new' pilot bushing from Kragen Auto was not quite in spec.
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