The K designation has the equivalent meaning of “revision” in Japanese. The original 74 CB550 had yet to be revised, so it didn’t get a K number, until the K1 was introduced. So, a K0 designation equates to no revision of the model.
However, In those days Honda was inconsistent in model or year documentation or specification. I would not bet money on no variation in production for first or early models. I think they mostly cared about how it looked like to the potential buyer. And dealers had to sort out the minutia.
Further, the design engineers didn’t build all the bikes. Production workers with quotas did with parts on the shelf. Design engineers didn’t write the published manuals or parts lists. The writers had to interpret what the engineers told them. While it would be nice, no one can guarantee accuracy of published lists, as no humans have infallibility as part of inherent make up. We just work with what we have.
