We arrived at port of Brooklyn back in May on Cunard. Getting thru customs was quick but the taxi line was very slow moving--single line for pickup and oddly enough, very few taxi's lined up, there was only 3 or 4 at a time qued up. It will be at least an hour drive from the port to LGA (don't believe the Google Map travel time estimates!--we left downtown Brooklyn on a Saturday for LGA and between construction, accidents and traffic it was a nail biter). If you dock on time and do the walk off with your luggage, you "should" be able to make it to the airport. If you can arrange a private transfer or Uber/Lyft, to have them there when you get off the ship, that would be the best option but entrance to the port is very controlled and I do not know if/where they allow Uber. Do you have TSA pre-check for LGA security? It will be cutting it very close!