Cougar's Unlimited LLC has a troubleshooting guide for 69-70 Shelby's on their website try that. It was helpful when I had a problem with my 69. They might even have the part you need. Or try calling them
http://www.thuntek.net/cougars_unlimited/69seqts.htm
http://www.thuntek.net/cougars_unlimited/69seqts.htm