- have to disagree. Are you basing your comment only on your one examples or do you have more vin's/cars to support it?
This is an October 65 build 66 Mustang that had an old starter cable assembly, C5ZB-14431-A, with two brackets and a "disintegrated" insulation sleeve, so I replaced it with a reproduction assembly of the same assembly number. I assume that I had a situation of Ford using up old stock, a 65 part on a 66. This was discussed with the two previous owners who told me what they had done to the car before I bought it. To continue this a bit further, 64 Mustangs, 260 and 289 engines, used part number C4ZF-14431-A (or -B) that is shown with one bracket in the 64 Electrical Assembly Manual. I again will state - one or two brackets depends on the assembly part number. An early 65 may have used a 64 cable to consume existing stock, hence one bracket.
When the part in question found on a car reflects the part number on the Ford Assembly Drawing, you have accept it as accurate. A picture might be worth a 1000 words, but the part number is the final deciding factor.
Jim