Holley 4346 vs 4053 base plates

[ko-lek-tor]

In J. MacNeish's book on 1969 Z28 and SS396 facts, pg. 141, and I quote, "The base plates are also slightly different." This is talking about the differences in the 4346 vs 4053 Holley carburetors after noting that the 4346 has a vent hole on the primary bowl and the 4053 does not.
So, what are different about these base plates?

[lynnbilodeau]

I would send Eric (vintagemusclecar) a message over on the Yenko site.