NY law enforcement sources tell us ... the NYPD has been struggling with manning the building since the election. The department's been drawing from various precincts, and it's been a little helter-skelter.

We're told the brass is now seriously considering cherry-picking 30 to 40 officers with solid records who don't take an excessive number of sick days to staff the area. Half would work the day shift -- 7 AM to 7 PM -- and the other half the night shift.

The advantage ... the officers would have familiarity with the area and any issues that pop up.

Obviously, there's a Secret Service element too, but guarding the building is part of the drill for the NYPD.

An NYPD spokesperson tells us they regularly reassess security measuring as well as staffing, and a number of options are under consideration.