AMK Products is the major manufacturer of original and repo fasteners. I'd bet everyone else is a reseller of their products. https://www.amkproducts.com/ The guys on 65gs.com put together an AMK hardware list for '65's. That may get you 95% of the correct hardware for a '66. I'd prefer to not post their list here, as it's not my work. You're a member there so you have access to it. I'll PM you the link. Or go thru the AMK catalog and match up your fasteners to their offerings. AMK does have kits for Chevelle and GTO that may get you close. Unfortunately Todd doesn't list much for pre-1970. He may be able to match fasteners for your 66 if you provide pictures or samples. BTW, most of the under hood hardware on a '66 is phosphate coated, not black oxide.
