I have come into possession of a 1971 Buick New Vehicle Warranty and Policy guide for VIN 454671Y149424. It came with a car I am in the process of getting running again. And it's not for the car I am working on. If you own the car with the Y149424 VIN I'll send it to you.
That's not from a 1971 Riviera. They were al built in Flint, MI so the 7th digit should say H instead of Y. And they started the production numbers for the 1971 Riviera with 900001. That VIN is from a model year 1971 LeSabre Custom convertible, built in Wilmington, DE.
I didn't even notice it wasn't a Riv VIN until you pointed it out. I still have the card and my offer still stands.