You could run a deck on a half ton safely/legally, but it would need to be a truck selected specifically for running a deck. Max payload package, bags, NOT a dumb 4 door/micro box. I'm not sure about Chevy or Dodge, but Ford has the 8200GVWR package available on their half tons. That package in an 8' box, regular cab or supercab, and it would more than likely do just fine. I do not think any quadcab/microbox truck is a good idea for more than one sled in the box, for the reason SkiDooinit explained above.
See this table:
http://www.ford.com/trucks/f150/specifications/payload/ not all half tons are created equal, and the popular configurations are not impressive with payloads capacities.