Ok, here are some pictures of a '74 Z28 air cleaner. The snorkles measure just a hair over 2 3/4" long, when measured down the middle of the snorkle, from the body to the end. The overall diameter is 15 1/4". There weren't any decals applied to the lid from the factory.
This air cleaner was an early version that was used on non-HEI cars. HEI was introduced in January 1974. The larger diameter of the HEI distributor forced Chevy to make a bigger "dent" in the air cleaner body for clearance. This difference may have forced a different part number to be applied to the HEI version, but I don't know if that is a fact.
I hope this helps.