I did notice Britpart will state if it's OEM and if so it's a little more expensive.

I just found some Nokian TRI 2 tires size 250/75/16 that I'm going to try. $125 a tire at Simple Tire w/free shipping. The are similar to the Michelin XZL maybe better I was told. They measure 8.5" wide and 30.8" in diameter.