I seriously doubt if there is a way you can find out about a units insulation values from the vin #.
Likewise, be sceptical about mfgrs claims of insulation values as these are commonly only accurate in areas without ductwork, tanks, slide floors or roofs, inside frame, to sum it up, a gimmick.
Even dual pane windows are suspect when ( always? ) their frames are the very heat conductive aluminum. Houses have not used aluminum framed windows since the early 60s or '50s So, Be prepared for condensation or use a dehumidifier to minimize wall panel damage or degradation of insulation values from damp insulation due to aluminum window frames.
Many towable makes have sealed heated bellies and tanks suitable for freezing temps into the teens F. I consider these 3 season rigs, that can make it through some chilly spells, but not through prolonged cold or below 0 F ( -20 C ) for more than a few hours.
There are a few exceptions.
For true cold weather units proofed against freezing, that also are reasonable to heat (or cool in hot weather) the list is shorter.
Explore Excel, Arctic Fox, King of the Road, Teton Homes, Double Tree, Newmar, a few others.
They will not be easy to find or cheap, but the build quality, comfort and cost to heat or cool will make up for your time and cost.