1. Guess I Wasn't very Clear, That Passageway is Connected to a Exhaust Port.
2. HOT Exhaust Gases WILL Come Shooting Out Of There!
3. You DO NOT Want the Bottom of the Carburetor to Be Constantly BLASTED with Extremely HOT Gases!
4. So PLUG IT! Or, use Intake Gaskets with the Port Closed-Off.
5. The adjacent Larger Hole with the Two smaller Holes, is for the Choke Heater COIL. Or, It too, must be Blocked Off. There are Parts for this.
6. Any Vacuum...went to the 'Vacuum DIAPHRAM MOTER', this controlled the EGR Valve that Had been Mounted on That EGR PLATE, mentioned earlier, and is now missing in your photo. In you case you don't need to worry about a Vacuum Source. Only Leaks to the Carb Base! Carry-On!
MJ