I have replaced most of the clutch head screws on my truck with hex head cap screws since I am not restoring to original.
Here is a link though to a fella who sells 'em, but they sure are pricey. Nice interactive website:
http://www.aaronstorxscrews.com/Aaron's Torx Screws
714 W. Angus Avenue
Suite E
Orange, CA 92868
Phone: 714-838-3575 or
877-838-3575
Fax: 714-838-3165