When Jim puts a box in the truck, we see him sit it on top of other items and it sticks up too high to be able to shut the hatch but immediately we switch camera angle, and she slams the hatch shut.
In Peter's math class, his teacher says that the students will need to know the quadratic formula to pass the regents exam. Regents exams are only given in New York State, and not in New Jersey, where the film is set.
The Datsun B210 (or 510?) Gabe is driving mysteriously has a new paint job and hubcap upon his departure to Florida at the conclusion - earlier scenes show a more beaten up vehicle.