My 66 is NOT original. The clamps are repops. There is two, and should only be one.
I can't remember if I replaced the cable with a repop or not, I think so.
BUT THE HEAT SHEATH IS WHITE WITH A BLACK STRIPE ON MINE AND IT IS ORIGINAL.
Don't want to get off topic with the white sheath, but that material is the same type as the license plate light wiring cover. Over time, the material can lose the dark black coating and turn white. Believe they were soaked in tar or something similar over a cloth.
That is real clean white sheath that tar (or something similar) came off equally without leaving a trace of any other substance. (Brian, how did you do this?)
The part number on my starter cable with two brackets (and a disintegrating black sheath and no trace of any other color) that came off my 66 "K" Fastback (San Jose Oct 65 build) was C5ZF-14431-A, a 65 assembly, which is in contradiction to the 66 part number, C6DF-14431-A, with a single bracket (attached on the front engine mount bolt).
Ref Osborn 1965 Mustang Electrical Assembly Manual, AM0008 pg 29 and pg 31 view B, and 1966 Mustang Electrical Assembly Manual, AM0013 pg34 and pg 36 view B. A "C5ZF-" assembly uses two, a "C6DF-" assembly uses one.
I attribute my 65 starter cable use to Ford using up inventory.
Jim