Is there a way to tell if this intake belongs to a 67-68 Z28?
Neither, looks to be a GM performance catalog intake. Not assembly line Winters Foundry piece.
The intake manifold in 1967 & 1968 also had the oil fill tube on the intake as shown in the photo below:
http://www.camaros.org/forum/index.php?topic=20919.0
I think that manifold is much later. Could have come from a GM crate motor. The squared off port exits give it away at a glance. Assy line intakes were plain.
It has the centraly located thermostat housing so it would work for a '69. Earlier Z/28 manifolds had an offset thermostat location that would not line of with the long water pump style '69 alternator bracket.
Chevy Bowtie Z28 Replacement Aluminum Intake SBC 10185024
If it was the real thing - my understanding is that the only way would be to remove the splash plate on the bottom side and get the date casting number off of it..
Otherwise as far as I know the real '67 and '68 versions of the 610's are virtually identical otherwise.
Big difference in the runner shape between the one shown and again any '610 version - plus as mentioned, the bowtie emblem and a lack of oil fill tube hole on the front as well!
Genuine intakes did not have a bow tie cast into it, among also missing the front oil filler tube.