Dear George, Michael, Dan, and mid-60s Buick parts hounds,
I want to say that looks pretty bad. I think a lot of early 60's will work even corvairs for the framing.
George you might be able to find something local and save yourself the shipping. Southern California is still classic car country and I believe the seats aren't Buick specific. You'll need some help from the guys on this board because some of the brackets are Buick specific. Still, you might be able to find a seat locally and bring it home yourself. That would spare you a hefty shipping fee for a bulky item.
Cheers, Edouard