01 should be PI iirc that was the year anything that was not PI already became PI. They're the same, pi heads are pi heads. Well... Make sure they have the same valve cover bolt count. 13 is Windsor, 11 is Romeo. Besides that they are identical.
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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 ****.