To me it looks like older intake on newer heads. Because the non EGR and or divorced choke intakes are better looking junkyard grabs but everybody only has smog iron 400s that still run. Just my .02. You can see the open heat port in the shadow just south of the big chrome flake on the valve cover flange.
For this in the past, I have cut away the center part of each side of a gasket, made a plate from sheetmetal to cover the head hole and put orange RTV under it. The intake and bolts clamp it down. Stainless would be optimal but steel will run for a spell before it burns through. Blocking just one side is all thats needed if I remember right, passenger side. The exhaust note may change slightly after blocking the passage and she may be more prone to carb icing.
For what its worth, I've heard of breaking up an old piston, melting it in a skillet and pouring the passage full of that. Carefully. Thats more careful than I've got but I do have smog heads on my 455.
Did I post in stealth mode or something? Block it off. I might have pics to explain if you don't understand but we can't help if ignored.