I am not 100% sure about those Cadillac campers, but I am willing to bet that they were crafted from retired "Professional Cars" (ambulances and hearses). I do know that a lot of them were converted back in the day due to their long wheelbases, heavy-duty frames, suspensions, brakes and driveline - and the fact that they could usually be bought for next to nothing at that time. If you wanted to go that route, I imagine you COULD use any of the "Ghost Busters" 1959 Cadillac Ecto 1 kits - it represents the real item's 1959 Miller-Meteor ambulance body fairly nicely and they are relatively easy to come by at this time.