a hot topic among buyers when I was searching was, "How much of this bike is original, how much is an alteration from how the bike originally came from the factory."
My personal feeling is 'original is better-looking but not an absolute necessity on many things, for my taste" and everyone has their own idea about that. As long as you are getting what you want, what you think you are buying. You will pay more for "all original" in general.
these bikes are all about looks so you will of course check the chrome for pitting, corrosion on the frame and engine. A lot of exhaust pipes had corrosion on the bottom, so get under there or take a mirror, feel the bottoms.
I am running into a lot of issues from disuse. A bike that is run regularily will have pliable seals and stuff not gummed up or about to crack or leak... vs one that is a garage queen.
I have done the clutch, brake, plugs, but still having problems with stuff that hasn't been touched in years; see my other threads.
Good luck and listen to the experts here - I am just a newbie owner and wanted to share my recent experience as no one else responded.