Hey Donny,
Just because the truck has duals, does not nessecarily make it a 1.5 ton. It could be both a larger 2 ton or a smaller 1 ton. As for the factory VIN, it should be printed on a piece of metal either on the firewall or on the driver's side door jam. This pannel will also give you the truck's GVW wich will allw you to determine if it is in fact a 1.5 Ton.
-Jason
