Look at this thread.
That's basically 35x11 tires on his truck.
I know you're trying hard to figure out how to dump a pile of money into the new mall crawler you're buying, but take a look at what it will take to put 40-44" tires on it and what you'd have to do to it to fit that size. 40's ain't going on with just a leveling kit, especially with a hauler bed like you want.
Honestly, if you want to build a monster truck, a 3500 is a better platform to do it with both cost and practicality wise (even though practicality has 0 to do with it, because a class 3-5 diesel truck is rendered just about useless sitting on a huge lift and wheels)
You're into military wheels/tires if you want to keep real load capacity or have it on LT tires and only able to carry it's own weight.
Car shows and maybe mud bogs if you want to mod it to put down enough power to propel a 10klb + truck across a mud pit.
It'll make a real monster truck if you want it to, but will be a bunch of work and supporting modifications to get there.