What is this hose nipple for? Can I plug it?

[rwogs]

I want to replace my carburetor for a 1972 chevy C10 250 CI engine that had a rebuild Rochester Carb (7042021) that lacked a linkage to used the power pump (except it was left in the carburetor and the hole for the linkage was plugged-looked factory). I see lots of Rochester replacement carbs out there, except they all have a hose nipple sticking out of a hole above the float bowl (see shiny picture), that my carb does not (see less clean picture). Does anyone know what the nipple is for? Can I plug it?