There are trucks and there are truck shaped cars. The law should differentiate between them. You want a truck exemption from fuel mileage - then it better be a truck.

If it is a truck then dents from loading and hauling cargo are normal (though cargo should be tied down). Likewise scratched paint caused by off road driving are normal things for trucks with 4 wheel drive (buy a 2 wheel drive if you are only driving on road). If it is a truck you cannot consider cosmetic damage in the value, if it is road worthy then the value is about how many hours are on the engine and nothing else. (this just killed the used and trade in market for trucks so if you buy one you better keep it for 15000 engine hours)