Not the same, but I bought a tandem axle trailer at an auction a couple of years ago. No title, just the auctioneer's bill of sale, and the consignment form signed by the former owner. Now, how to get this registered and a plate issued?
I went to the Secretary of State's office and got the info needed. Had to get an official weigh slip for it and present that with my sale documents. They explained that they would issue a vehicle ID number or VIN for the trailer. That will be permanent. The registration and plate were issued thereafter as normal.
Now, one thing I don't know is if your title or paperwork says non road vehicle, what exactly your state requires to update that to road legal. I know if you apply to have a salvage vehicle title changed to a regular title, the State Police must inspect the vehicle and all repairs made to return it to non salvage condition.
Best to go on line or make a trip to your DMV with questions. States love to produce pamphlets and rule books.