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.
Corvette by the numbers says "most aluminum intakes have dates cast into the underside of the intake, usually under the oil splash shield." Note the use of the words "most" and "usually".
To check the date code you have to gently pry out the rivets holding the splash shield on. They can then be driven back in after checking it. The date code is in such a difficult position to read (remove manifold and splash shield) I would take the best manifold you can find. Only you, and the possibly the guy you bought it from, will know.
I sold a dated manifold to guy and had to tell him how to find the code. After he had received it he called and gave me a hard time for giving bogus info on Ebay. There is a "Dymo tape" number cast in which is in plain view and he thought that was the date code casting.