I've wrestled though identifying a few bolts as I worked on my '68. It is sometimes tedious. The Pontiac Parts Catalog often (but not always) shows fasteners in the Illustrations Sections. (I use the 1972 version that I got from Bishko) Sometimes you then have to dig into the part groups in the catalog's Parts Sections to obtain the application, finish, hardness, or other details.

I believe an on-line version of 1st gen applicable pages may still be available on line somewhere.