Best vacuum spot for the Brake booster ?

[Steve Cole]

I have an Edelbrock 1407 carb and a Edelbrock RPM Air Gap intake. My center vacuum port (front) is for the PCV, the passenger side smaller port is for distributor vacuum advance, the rear port is for the vacuum modulator on my t400. My valve covers contain the PCV and a breather/oil fill. I am assuming I need to tap directly into the manifold for the booster, but where ? There is a threaded port in the back center area that may work but I don't know for sure.

Can anyone point me in the right direction?
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