I don't know if Texas is the same, but in MN you would just register it as a truck according to the weight rating of the chassis. Doesn't have to be a commercial vehicle. MN has "Apportioned" plates for commercial trucks. Then they have "truck" plates for anything over 3/4 ton. I would think Texas would have similar registrations. The problem you then run into is likely the chassis is rated for 33k lbs. That would then probably make it illegal to drive with a normal class D license (or whatever TX uses for their base class). In MN we can go to 26k lbs on a class D.
'03 Freightliner FL112, 295" wheel base, with '03 United Specialties 26' living quarters, single screw, Cat C12 430 h/p 1650 torque, Eaton 10speed , 3.42 rear axle ratio