I believe that everything on my '71 750 is stock. The only thing I question is the seat. It has a smooth top instead of the diamond pattern I typically see.
I have the same seat and am curious as well but I don't think it's stock. All of the earlier stock K's I've seen have the pattern on top. An early after-market replacement maybe?
I've come close to pulling the trigger multiple times for a true stock seat but, not doing a full restore, I can't justify dropping a lot of money when I have a perfectly good seat.
I think the current one looks boss anyway.