The "300" is the code of the early CB 750 Four. Unusual is that they all end in "970" which must be the reference to the CR750. How helpful it would be if such parts would still be available.
I think that we simply misunderstand each other: by factory option, I am referring to options that the various models would come with from the factory. None of these parts qualify. You could not order any of the street bikes with these options from the factory directly. But if you knew the part numbers, surely the shop would order them and do the conversion for you, just as they would put another handle bar on your new bike if you so desired. But even back then, who really knew these numbers? I don't think most guys in the shop knew. I guess, that's why people turned to alternatives, like Lockhard (immensely popular back then). I don't know when these parts became unavailable, but I know that they would sell like hot cakes today--and they probably would have back then since the single disc is atrocious.
Anyhow, even without these parts being available today, you still can do the conversion with genuine Honda parts, including Honda steel lines. But it always is a conversion, a change of the original factory bike and not a factory option. It's not original although its Honda and contemporary. And that was my point. It's original only for the CR.
Anyway, thanks for these numbers. Just like the Japanese specs K7 with its rear disc brake, it's these little details that make this forum so interesting.
