I have done the same many times, if you go straight to your restaurant and it is midtown or similar then there is a good chance you will make it. Now this assumes an on time arrival (earlier is better):
- land 5.45 pm
- disembark 6 pm if lucky and in Upper
- walk and queue at immigration say 1hr 15mins average
- bags waiting on belt pick up and ten minutes later get into prebooked car (not a taxi)
- drive into Manhattan up to 1 hr 15 mins
- arrive restaurant 830 pm
It is possible, it's also possible the sod's law will interrupt but I have made 830 pm dinners off the VS045 before with a hit rate of say 70% and then others up to 30 mins late.
Of course, if you don't want to risk it, go for 930 [:D].
There's a plane at JFK, to fly you back from far away
all those dark and frantic transatlantic miles