"The chain doesn't have a master link. The fuel line has been replaced, but the carb overflow lines were original when I got it but they crumbled when I removed the float bowls to service the carbs. I have the remains in a box, but used new ones.
The tires appeared original when I got the bike! Rock hard, had to cut them off. Here is a pic of the old and new tire:"
then I would say that chain is the original factory supplied chain. In my 550F owner's manual, it talks about servicing the "endless" chain. Maybe yours does also.
Many of those didn't survive because back in the day, patching a back tire tube in the middle of nowhere was 10 times easier if you had removed a link and added a master link for easy chain removal.
Aslo, I don't think anyone sells endless chains....
Tires...original tires are identified by a sticker on the bike and the owners manual stating tire brand and size....at least on my '75....once again, not familiar with K0 500's....