we have avoided any gvw discussions by registering the truck as a motorhome
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You're fine on your existing truck, not only because you registered it as a motorhome, but because I'm guessing that the GVWR is not high enough to need a commercial license.

You were mentioning trying to find something that would allow you to put two cars inside a 32' box mounted on a truck. I was bringing up the point of smaller tires (that would get you low enough to the ground) not allowing for the needed GVWR to carry two cars. GVWR is only going to be as high as the weakest link.

Your current truck sounds like a neat setup.