Title and/or Registration both prove ownership, you still must have one or the other to transfer it to a new owner, and either/both must have a unique serial # that matches the number stamped into the frame at the factory. Most states have a process to issue a new/replacement title to a vehicle where there is no serial number such as when a handbuilt chassis, the front portion of the chassis where the umber was originally stamped has been replaced or a different frame was used. This usually requires a great deal of paperwork, receipts for all the major components, a bond to be posted, an inspection by a DMV or law enforcement officer, a records search to verify it is not stolen and then a new serial number is issued and stamped into the chassis. Typically the vehicle is now classified not as "53 Ford F100" but as a 2014 Homebuilt, Salvage, or something similar which can make it difficult to resell, insure, get inspected, or value if your state charges a tax or registration based on value. If anything comes up hokey the state can confiscate the vehicle without any compensation.