That "hole" is a manifold vac vac tap. Some GM applications used that location to run the power brake booster, in some model years. If your engine has the vac tap for the power brakes on an intake manifold runner, keep that and PLUG the hole in the carb with a supplied pipe plug in the bag of goodies (the plug, hose clamps, studs, nuts, etc.) which should have come with the carb. The instruction sheet should cover what the vac taps on the front go to (1 for ported vac to the distributor, 1 for full manifold vac, and the big on in the middle for pcv.
Be sure to hook the elec choke to a switched 12V power source. Might need to adjust the choke thermostat coil a bit leaner to get it to come off soon enough.
Putting that carb on a spreadbore (TQuad) manifold, you'll need the appropriate adapter unless you are replacing the intake manifold with an aftermarket Edelbrock (or similar) which has a mounting area which will support both styles of carburetors.
Enjoy!
CBODY67
