I hate to tell you this, but if you mount the 33 x 12.5's on stock rims you have voided the tire manufacturers warranty. All manufacturers spec a minimum of 8.5 in. rim width. Stock rims are a maximum 7.5 in. A 31 x 10.5 will fit stock rims.
You will have people say they have them mounted on stock rims and it is physically possible to stuff them on stock rims. HOWEVER, you run the risk of popping a bead which means instant flat. If you do that and it results in an accident, perhaps a serious one which may result in someones death, you will be on your own. The manufacturer is not responsible for using tires outside of their specifications.
My suggestion to you, is: Since you are going to spend in excess of $500.00 on nice looking tires, wait untill you have the proper wheels to mount them on. Your truck may also need atleast a 3" lift to prevent them from getting ruined by the edges of the wheel wells cutting the tread when the suspension flexs. Even with the lift, there will most likely be slight rubbing in the front on the radius arms in hard over turns, solution: "Don't do that".
Good luck,
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