Hi Eric
Surprised none of the Ford guys on MLU could not answer this one off the top of their heads. But then I pulled out my only Ford parts book an saw that there maybe different ones. When I looked at one of the North American Ford Parts sites (
http://macsautoparts.com/search.asp?...action=showall ) it lists several different ones and several different diameters.
Hope this helps, if you were working on a Chevy I could go out and look at the number on the parts box.
Cheers Phil