2536771 CAP 4BBL Intake Manifold Port Plug ?

OK I thought I had this figured out but I was wrong. I can not seem to find the right plug to block off this vacuum port on this CAP intake manifold, the bigger one that is right behind the carb. Does anyone have a picture of what ever was in that port from the factory and does anyone know the proper size plug that can be used to block it off. Take a look and if you can help I would appreciate it.
Thanks
Bob

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