You will need a MSO (manufacturer's certificate of origin) for the major components such as frame kit, receipts for all major new parts, and receipts with VIN for all major used parts. The State will issue a "VIN" and the title will be issued as "New-assembled from parts" It will also require an inspection by the state DMV. (I do this all the time with motorcycles) Sometimes it is easier to have a licensed custom builder certify it and assign a VIN. (for a fee of course) Another option in NY for a pre-74 would be to find a registration for a junked car the same year as your custom body. Transfer it to you, as long as the original registration has not been issued a certificate of destruction. Then register your custom as the one you have the new transferrable registration for. Keep the original body ID plate and attach it to your rod for your annual inspection. You have restored your junker by replacing everything. (step 1 in NY is verify the serial or VIN, after removing old inspection sticker) The state's objective is to maintain a paper trail. They can really make it difficult sometimes. My last project took me 4 months to get the paper trail correct.