We may have previously discussed that Y21 was for conforming with the "Moroney Price Label" (Federal) consumer protection law that made sure there were no hidden or missing items and clearly spelled out what the customer was paying for and getting. I think there was special documentation requirements and the fender tag needed to say it was originally a 383 engine with the A12 special V-8 conversion. There was a cover letter to all of the A12 package documentation that specifically stated that this Special Sales Order needed to have specific documentation and the Moroney Price Label (aka window sticker) had to have certain info on it and that the Moroney Price Label info had to be reported to Car Division Service Department and a special warranty book would be provided by the factory.