One major drawback to a tire that wide is going to be VERY squirrely handling every time it rains. There's just nowhere near enough weight on the back end of a stovebolt pickup to keep a wide tire planted tight to wet pavement. Maybe if you made the bed floor from 3/8" steel plate- - - - - - -!!!!!!
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!