Mattax said

Yes 600 cfm model 4160


Vacuum sources are like this.
View attachment 1715857826
There usually is another small manifold vacuum port on the front of the carburator's baseplate.


The three threaded holes are for mounting a choke.
The circled hole is the location for the choke qualification passage. That's a vacuum source that opens the choke further when the engine starts running. Whether it is drilled through, you'll have to check.
I've also seen some older Holley's use that as part of a hot air supply to the choke. I doubt yours has that function.
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