Do you still have the original engine? There a chance your truck was originally titled using the engine serial number (stamped on the flat pad next to the distributor), this number is different than the body number. If that's the way it was originally titled then your body serial number is not in any DMV data base.
As mentioned above you need to put the tag back on as the inspectors may not approve your title request if it shows signs of being tampered with.
Mike B
