Where to hook up Vacuum Gauge

[Mils]

I have a 427 S/O with 2 Holley (List 1849) 4160's that were just rebuilt. I'm experiencing some hesitation and minor backfires on passenger side during mid-range acceleration. I want to check for vacuum leaks and set the lean/rich screw's to optimal settings, but i have no idea where to hook up my gauge. These carbs do not have a manifold vacuum port on the throttle base. I'm at a loss. Any ideas?

[Bernica]

Look for a plug on the manifold that you can remove and install a temporary hose nipple. When finished, either remove the nipple and re-plug or just put a cap over it.
My 2 c...

[FWB]

the manifold ports are about in the center on each side of the manifold.
i keep a hose fitting in one on mine and cap when not in use