I remember seeing mentions across the internet that GM has no records left of that era (off the top of my head, their earliest records date from a VIN number format change, either late 70s or early 80s). This is what allowed a cottage industry to develop, turning not-so-special C2s into highly-optioned rarities, and this is why cars sold with original documentation (order sheet showing the option list, original window sticker, etc...) tend to command higher prices.
There is a lot of information in the NCRS judging guides (one per model year) to decipher build codes and determine build or cast dates of the different components. A lot of that information can be found scattered on the net, too: the US forum corvetteforum.com is a good source if you're not afraid to spend some time playing with the "advanced search" page... The NCRS can also issue a document that indicates, based on the VIN, where a car was delivered (dealer number) and when.
I hope this helps, good luck with your research work!