Tim, the rod from the shifter to the manual shift arm on your C6 is D1ZZ-7326-B (ID# D1ZA-7340-BA). It is 18" in length and identified by a red paint daub. To my knowledge they are not reproduced and used ones can be tough to find. I would give Don @ Ohio Mustang Supply or Mike @ Motor City Mustang a try since they both have parts cars.
If none show up you might look at the 72-73 version D2ZZ-7326-A (ID# D2ZA-7340-AA) It is a little shorter at 17 1/2" and also marked with a red paint daub. At least these are stamped with the ID# and not just the paint daub which after 40+ years may not be visible.
Thank you much Steve for the picture, data and specs. Very helpful and very appreciated. The data will help me track one down. Tim