Rust sucks. I would look underneath and see how bad it looks under there rust wise. The lockers and head gasket is big. Who did the head gasket? Has there been any maintenance on the front end? I think that is as big as any item. How does the front end look (seeping)?
Slee has a buyers guide. Go to their site and learn as much as you can.
Honestly, he's not gonna get that price and if the rust isn't too bad, it might be doable. But if there is visible rust underneath, avoid it.
I bought one car from the east coast..it has some rust/corrosion on the undercarriage. Hate it. Not good for anything. If the car is replaceable and you can find it elsewhere (as you can an 80), stay away...IMO.