Never heard of a 337? Maybe you mean 347? If so its going to be hard to tell if it is a true 347 due to a 347 being a stroked 302! I would test drive and see how fast is. A healthy 347 should pull you back pretty good. Common rust areas are the trunk, door wells, inner fender wells, pop the hood check the engine bay for scuffs, rust, over spray. Buying a used older car can be a nightmare good luck to you.