I would personally mention that I think it good to keep the duals on the back.
I have driven dump trucks for a few years, and I was constantly getting rocks in there. It really is not a big deal. Just carry a chain with you that is long enough to reach from the back tip of the rear tire to the front tip of the front tire plus a couple feet. (hook on each end of the chain).
Then you roll the tire until the rock is facing the front tire, wrap the chain around it, and place the other end under the front tire. Back up, rock pops out. Now you are better off if someone can watch the rock and see if it might damage the tire (rare). If it is sharp and may damage the tire a few good blows with a five lbs hand held sledge hammer with typically fracture the rock into more manageable sizes. It really is not that big of a deal. I had to do this at least once a month. Also it would be good to know that I was driving on construction sites, not well used dirt roads. IE you are not as likely to get a rock in the tires if you just watch where you are going and avoid driving on rocks that will get stuck in there. (obviously some roads you can not miss them, but really, just drive smart and you should be alright.)
Another important consideration of the duals is a flat tire. I have seen guys more than a few times drive with three rear tires. For instance, my boss got a flat one day, he popped off the offending tire, and drove two hours to the nearest tire shop. You can't be doing that with super singles. You are just stuck there, with what ever help happens to pass you by, and is willing to take you two hours away to a new tire, and then willing and able to haul you and said tire back to your bus.
Change of use (to an RV) you should be required a few typical things... Permanently mounted Sink, Toilet, dinning space, bed, etc. Most states have four or five things that they require to be in there to be able to call it a motorhome. That should be easy enough to find.
Here it is...
www.dmv.ca.gov said:
A "house car" is a motor vehicle originally designed, or permanently altered, and equipped for human habitation, or to which a camper has been permanently attached. A motor vehicle to which a camper has been temporarily attached is not a house car except that, for the purposes of Division 11 (commencing with Section 21000) and Division 12 (commencing with Section 24000), a motor vehicle equipped with a camper having an axle that is designed to support a portion of the weight of the camper unit shall be considered a three-axle house car regardless of the method of attachment or manner of registration. A house car shall not be deemed to be a motortruck.
Here is the link to the page I found this on...
http://www.dmv.ca.gov/pubs/vctop/d01/vc362.htm
This is all from California,
Texas has this to say.
Used trucks, truck-tractor and buses, which have been reconstructed or converted to contain living quarters, should title as Motor Homes and register with passenger plates. Owners should support the title application with a photograph of the interior and exterior, a weight certificate verifying the gross weight, and a Rebuilt Vehicle Statement, Form VTR-61 explaining the alteration. The make, year model, and vehicle identification number should be the same as that shown on the title covering the truck, truck-tractor or bus.
Note: When the certificate of title is issued for this type of vehicle, the notation “Reconstructed” appears.
www.jackdanmayer.com said:
- You need some pictures of the tractor. Front and side views, at a minimum. I went armed with all four sides, but they only used the front view. You cannot register without this.
- You also need pictures of the modifications you have made to the tractor to turn it into a motor home. I used pictures of the bed, the refrigerator, the microwave, and permanent shore power. Along with this you need a written statement of your modifications, and that they are permanent (I hand wrote it on the spot). There was no inspection of any of these items in my case, and I know of no one who has encountered inspections. It is the county tax people who issue the title and registration and they are mainly interested in your $, in my opinion.
Here is the link to that one
http://www.jackdanmayer.com/registration_and_legal_issues.htm
Just have a search around, and I am sure you can find what you need for your state.
I hope that helps.
Regards,
Brian
) i think i would seriously consider to swap to a single rear tire like the General Grabber OA wide base 385/65/22.5. 
