I found this photo of a '65 Skylark GS engine bay from a Buick showroom literature piece introducting the 1965 GSs. It's shows a red positive battery cable. The photo is not clear enough to tell if it has spring ring or clamp style ends.
But as mention earlier, what the factory installed is not always the same thing as NOS parts sold over the dealership parts counter. With the NOS inventory that Mark has and his years of experience with automotive parts, I think this can only be the logical explanation.
Regarding M & H , I don't understand why they couldn't make a cable the correct length for a '65 and or have a choice as to what style of cable ends you want. Because of :occasion16:the longer delivery time when ordering, they probably don't keep an inventory, but rather make them as the order comes in (especially for the rare apps).
John