My manifold has the open sided choke well on it So maybe the exhaust has been changed at some point. Thats why the different choke. Are all open side wells for electric choke? Would do no good to add a regular choke if it is open on the side.
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Here's a photo of a couple non-heat assist chokes for a slant 1bbl.. The Carter is on the left and the Holley is on the right.