The 6.75 traction lock was only offered, I believe, as a dealer installed option on the mustangii. Read an article about it in CarCraft years ago. Hence, I doubt too many are out there. They do pop up though as I happen to have an NOS one. I also ran across a set of NOS Schieffer 3.70 gears. I haven't seen any 4.11s since Midwest Auto advertised them back in the early 80s. Good luck with your search. JT