Question about Edelbrock carbs

Hi guys, i just have a quick question regarding eddy carbs. I have dual eddy's on my tunnel rammed 360, while doing some work on the car today i noticed that the rear carb (part# ed-1803), has an exposed hole that's sucking in air, the front one has what looks like a brass plug? Front one is mechanical choke and rear one electric (although elec choke removed). Would like to know what's going on with this, and looking at my old pics, seems like there never was anything there to plug it.
Any info greatly appreciated as always, thanks.
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