It turns out I hate all pickup manufacturers

This is what you need. A Super Camper Special. Those trucks were designed to do EXACTLY what you are looking for. Notice how far back the rear axle is. That's for increased load capacity. No other truck maker did that. You won't find a heavier duty old model truck. That looks like a goodun, too.

http://spokane.craigslist.org/cto/4943249794.html