Hi All,
Well, if anyone's interested, I got a hold of the guy after a little bit of email swapping and phone tag. Despite coming off as kind of a jerk on the email responses, he was actually a helpful guy. Turns out his father bought the 550 as a used bike in the early 80's, kept it for years until he got too old to ride, and gave it to this guy, his son. It sat for a couple of years, then about 5 years ago, this guy cleaned/restored/tuned up the bike. New sprockets, chains, exhaust, replaced a fair amount of the chrome work, cleaned out carbs and tank, rebuilt front brake, points, plugs, wires etc etc. and did one hell of a cleaning and polishing job. Sounds like a great story, obviously don't know true it is.
He's seems negotiable on the price, to a point, but I didn't push it on the phone, and he'll also throw in a single bike trailer for my troubles. What a guy. I must appear to be a nice guy on the phone. So assuming we're not in blizzard conditions again this weekend, I was going to slide over to Chicago this weekend and check it out.
Thanks again for your help,
Paul