If you restore a car, I can guarantee you that you will not have every part genuine GM. (Anyone have an NOS W-25 air cleaner seal on the shelf?) And if you wanted it period-correct, your car would never win a trophy because of the so-so quality of the builds back then wouldn't hold up to the scrutiny of what's out there now. Most call them "over-restored"

Most high-quality restorations are meticulously mapped out, planned, then executed in a manner way outside the business model of mass production. What took GM a matter of days on an assembly line, some people take years. But it's only original once.

I'll take a high-quality reproduction part in a heartbeat if it looks/feels like original. And if I can't find a nice original, I'll take what I can live with, even if it isn't perfect.