Probably just a late 340 log. Not the better 68 casting. but they were the fastest thing on the road in 76 (?), I think a 454 truck was up there too! Vette was neutered by that time.
74-72 is basically the same. 75 is different on the drivers side as it has a bell like the pass side. 76 I’m not sure, but I would suspect there the same as 75. I could take some pics of mine that are on a car. Kim
Here is some pics of the manifolds. I couldn’t get a decent shot of the flanges but both manifolds have a bell on them There is also a cross over pipe at the rear from 1side to the other. I didn’t get any underneath pics. Kim