What Size Truck?

You don't need to limit yourself to one tons for that size fiver. Since you're buying used that's an important point to consider as it would eliminate a significant percentage of inventory that's available. Tire and axle ratings are the critical limits you need to consider on 3/4 tons, much more so than the payload which is nothing more than GVWR minus curb weight at the factory - in many cases it means nothing.