Technically the lower receiver is considered a firearm. ("other" on a 4473.) So if he does bring just the lower into NY with a collapsible stock that is two evil parts(stock + pistol grip). Thats unless he says the upper is a bolt action upper and its not semi!!! lol. The laws are as dumb as they get. But thats what happens when you let rich Harvard book nerds run the place with no real time on experience.^ That ^
As long as you're not moving to NYC anyway.
If you've someone in VA who will do it, you can bring your lower and leave your upper behind to give you more time to decide how you want to go about meeting compliance, then have them ship the upper to you. (its legal to ship an upper via UPS. But just call it 'machine parts' if asked as sometimes things like that dissapear off the trucks)
You can have a functional carbine stock on a lower receiver all day long. It's just when you put an upper on it things get stupid(er)
Alternatively, you could drop the whole thing off at someplace like Allstar Tactical on your way through and they can make things compliant.
From there you can go back and pick it up, or have them ship to a FFL near where you're going to end up.
Just to ask: was your rifle manufactured prior to September 1994?
If so, then you don't have to tweak nuthin as its preban and therefore exempt from the NYAWB.