oversize tire

[fettvenne]

hello, i need to change my tire, my tire size is 235/75/15, i found 4 tires 31x10.5x15, the guys who sold it said that will fit on my original rims, but i'm not sure, it's very large, Do i need spacer to put this tire? My truck have not suspension kit, he's original...This tire was used but in very good shape and it was mud tire...I don't what to put new tire because i need to change all bushing on my rear differential, so i can't do alignement on the truck, i change tire because it very finish.