It is possible to make the connection if you land on time, T8 is faster than T7. But if you are 10 minutes late you are going to be staying the night in New York. If you are going to Vegas it may still be a better gamble than some alternatives! The baggage will need to be rechecked at T8, but it's just a matter of going from one carousel to another with customs in between. Go HBO to improve your chances in the lottery of life. So if missing one night in LAS is not acceptable, you need to rebook, I'd give you a 70% chance of making it, 80% if HBO.