Newbie with some general Qs

Ahoy - long-time reader, first-time poster here. Tomorrow I am going to look at a supposedly top notch '83 550LTD and was wondering what common problems, if any, to look for. The bike honestly looks great from the posted pics (Craigslist of course) and the seller runs a motorcycle repair business, so in theory the bike should be in excellent running condition as he states in the ad. However, the asking price is pretty steep even in today's motorcycle seller's market ($1500) and there's no mention of the bike's mileage in the ad.

The recent mods/repairs to the bike include a fresh coat of paint, brake job, titanium clutch, sport handlebars, new header/exhaust, race pistons (?), full tune-up including carb cleaning and re-jet. What else to check before buying? The guy claims it's capable of 130mph and 70mpg, though I doubt it can do either of those with my bulky ass on its back.

Titanium Clutch? New one to me. What Header? New Exhaust? Aftermarket is limited to these bikes, ebay is your best friend. Don't go by the 130/170 mph. You can't have both. Mine with a stage 3 jetting, and pod fiters, with 4-1 exhaust still gets ~60 mpg. Theoretically I can go 149 mph, but that's not gong to happen, and still get my 60 mpg.

Have fun!