If the tire sidewalls aren't actually touching each other, you're good to go, even if they're running pretty close together. Keep the tires aired up to the reccomended pressure molded into the sidewalls so they don't bulge and contact each other with the truck loaded.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!