Howdy Benzie,
Hard tops are usually on the commercial vehicles when they have implements on them. Look for rust along the lower edge under the headlights and the back corners of the cab.Also try to get a vin number. If they have the paper work they should have it. It might not be called a vin but it should be. You might be able to find it onthe truck. I think it might be on the frame on the passenger side towards the front. Well have fun dreaming Mog dreams