Ok I got the answers. My son is a off road nuts and rebuilds engines. He was wondering too, so he got in hold of the big tires guys who works on semis and pick ups. there is few cons of using those tires.
1 is the capacity limit. I will lose about 700bls. they said my camper (5000bls load) is a bit too heavy for those tires.
2 is if flat, possilily will damage the fenders. and where will I put the spare one? its illegally to carry it in front of your truck in Colorado. the two tires on one side if one is flat the second will help hold it till I replace the flat.
3 cost more than the two tires put together!
4 not good in rain snow or mud. dually tires with camper has a lot better traction then those super wide single tire.
So I was told its much better to keep it as is with the dually tires and much safer.
so I guess I stick with the ones I have. many thanks guys for your time. have a good Christmas time wherever you are.