New Jersey is one of the "interesting" states to say the least...
I have many cars legally registered there, but I cannot say that any one experience has been the same. I've had some that recognized the 9 digit chassis number as a VIN, some that have been assigned a VIN, some that have had to go through emissions testing, some only safety standards testing. I've had customers who have been told they had to add a low lever sensor in the brake reservoir, some who have had to show official documentation on the integrity if the fuel line, some who have had to show documentation on the Lexan used in the side curtains, and the list goes on. The kicker is that for each one of these cases I have just as many (or more) that have been in and out in one trip... no questions asked.
As I'm sure you can imagine, it makes it very difficult when you really don't know what to expect. That's why I love those SEMA states! Or even states that just set rules and then FOLLOW them. Even if I don;t like all of the rules, at least I can know what is expected!
So... I guess the answer to NJ registration is more "luck of the draw" than any one thing.