When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Check the battery cables. Some C3 years used copper-plated aluminum cables, which are utter garbage. My 77 factory cables were this way. AC Delco makes good replacement cables in 100% copper which are available from most (if not all) Corvette vendors. Changing the long + cable is a PITA, though.