Thanks for the lead, I'll check it out.
And seeing that this is your first post, welcome!
+1, and WELCOME! Very seldom does a new member introduce themselves with "HELP OFFERED", usually a new member has a request for "HELP NEEDED"! Much thanks!
Ebay auction # 321117488484 claims to be the correct early "thinner" stripe GT kit for '67.
This^^^ IS the previously mentioned Class-Tec in Virginia, Chad White (the owner). 540-696-5758.
I already ordered a set earlier this morning. I see Chad also offers a set of the typically found (wider) version as well and has other Mustang stripe kits for multiple years and applications with a notation of Ford Licensed.
The seller acknowledged the order immediately, giving POS feedback within a few minutes. I requested the dimensions to be verified or they will be returned. My request for verification asks that they be "narrow stripes that are 3/8" wide (Not 1/2") a wide stripe that are 1-15/32"(Not 1-1/2") and the gaps between the narrow and wide stripes are 9/32" wide each." and the seller did not rebut. I will offer an image of the product alongside a NOS Ford set I have.