75 Dodge Dart?

Look in the trunk for rot. Wheel well and everything else in the trunk, the underside of the rear 1/4s, under the viynl top (Poke at it with finger all over if you hear crunching it has rust under it) if it has one, and the rocker panels, If you see bubbleing in the bottoms of 1/4's or fenders rust.
Just look just about everywhere.
Keep us posted if you buy it.