Pictured are the two different types. Is there any performance difference? The one on the right is nicer to look at.
Those were used on the 660 tunnel ram/dual quad race applications. You can get them separately from Holley. I used use those on all my carb builds as they have that hole for more flow.The one on the right also has mounting screws shown that have a larger through-hole for larger diameter jets.
Have a white cam in there now.