I found a similar clip in my junk box. I believe the part number is 358362-S, as shown in the 67 Electrical Assembly Manual, AM0018 pg 76, and is used on A/C equipped Mustangs (all engines) from 67 thru 70, but I have found no supporting documentation, drawings or specs. If someone can measure the "grip" and overall length that would make identification easier. Pictures later. I have some appointments this morning first.
Jim