If you want to make a small amount of cash selling an old truck, start with large amount....
reading between the lines, it looks like you may be trying to get rid of your truck and are looking for suggestions. As was mentioned, the 1/2 tons seem to sell easier as people want to either restore them or rod them. The 3/4 and larger are usually picked up by people that like old iron, may restore them, however usually use them as trucks.