Threaded vaccum port on 2Bbl Intake

[roadrunnerh]

Hey folks, Can someone verify the size of the threaded port on my 225 Intake manifold. I want to buy a plug on my way home from work.
Is it 1/2"NPT, 5/8"NPT?

 

[powerwagonpaul]

I believe it is a 3/8" npt thread