What are the holes on the backside of this carburetor for?

What are the top oblong hole and the tall long hole/indenture used for? Please ignore the round black dot, I did that with a marks a lot, was thinking about drilling hole there but changed my mind. Reason I ask is I was thinking about filling it in with JB Weld as that top oblong hole sticks out above the intake manifold just a little enough so I can slip a paper clip in it. It is only covered by the gasket not metal/gasket/metal when bolted on. I would leave the intake side alone and it would still be open to both carb barrels.
Any help appreciated.

Looks like you got you an early to mid 80’s Johnyrude there. Gotta believe that void in the center is just part of the mold and serves no purpose, the oblong hole on top is probably a vent. I think i’d take it easy with the JB...

Thanks was thinking the lower was just for mold too. Now the upper has no hole inside the hole, it is just an indenture, that is suppose to match up with the intake and probably vent gases? If I seal it up the intake hole and indenture to both barrels would still be open. Your right 1981 Evinrude 115hp carbs trying to mount on a 1978 Johnson 115 powerhead and run fuel primer lines to the bypass covers.

If it doesn’t lead anywhere, then i’d say that is just part of the mold also. Don’t believe i’d worry about modifying anything, hopefully I’m understanding this correctly.