Just to add to you all's future tire options, pitbull tires makes some 39.5x16.5 and even wider 44x19.5's. More aggressive tread than the cepeks, but not as large lug voids as the swampers. If you decide to go 44+ they make a 47x21 "growler" that looks like it would be a good fit for your needs.
http://www.pitbulltires.com/index_02.php
http://www.pitbulltires.com/index_02.php