I have the GM 1974 service manual with the 1975 supplement, and the GM assembly manual. The assembly manual designates a part number to each fastener but does not give any "generic" information. I bought this car in a basket, guess I'll figure it out somehow. It is kind of tough when I have never seen it in one piece.
As I have my own fastener business and am I c3 owner I'd be happy to help you out.
For instance if you tell me you want all the bolts for the rear crossmember in stainless steel thats all I'd need. The catalogs charge ridiculous prices for these because they are "corvette".
I am an ARP dealer as well. www.titaniumfasteners.com
The only place you're going to find that kind of detail fastener information for your car is in the NCRS 1975-77 Corvette Technical Information Manual & Judging Guide. You can order it on-line at www.ncrs.org or by phone at (513) 385-8526. It will tell you size, headmark, and finish information for most of the fasteners. Parts books won't help much, as very few production fasteners were ever available through service.