Fun fact: 320 park and the building to it's right were "twins" at one point!
Sometime in the 90's the building was reclad and got it's height extended. If I'm correct the zoning in this particular area allows buildings to be added on, but if they were torn down completely the new structure would have to be
smaller. (I saw a thread on here about another proposal for park Ave -forgot the name - that involves tearing down another building partially and building up from there for that very reason.) EDIT:
HERE IT IS
That weird zoning quirk is set to be resolved in that "midtown rezoning plan" that's been proposed....
Sorry for going OT just want to try and clear that up