RUST

I hate that word
Yeah the coupes love to rust it up like there’s no tomorrow, but hey most cars that have been around for 30 odd years would do the same I guess.
One thing I suggest you do is take a small fridge magnet with you when looking at the car. One of those annoying advertising ones you get in the mail for your local real-estate agent. You know the type.. slim, small, with their number printed all over it. Mainly because this magnet is rather weak and for what you are about to do with it is a lot better.
Place the magnet on various parts on the quarters of the car, if it sticks nicely you can tell its metal, if it falls off in parts or doesn’t really stick strongly then you more than likely have bog in that part.
Also make sure the body is straight. Things like interior and motor parts are replaceable, but to find a nice straight clean body is almost as rare as hen’s teeth these days. How much are you willing to part with for an XB GT?
Anyway, happy hunting mate.