"No disrespect to Willie either, but there have been several people build AR's and similar in NJ, and its rare that I have heard of a problem, unless the firearm has features that are prohibited."
You haven't lived until you've spent a week in the lockup in Patterson.
Trust Old Willie on that. This incident occured long before the Federal AWB or even NJ's earlier AWB was placed into effect, so there were no prohibited features at play. And in the end, after $K$'s and many months were spent, all was well and I was let go with a warning (and a serious case of the ass for the legal system in general and the NJ Legal System in particular). That low opinion has been reinforced occasionally over the years, but those are other stories.
This incident took place, however, during the period when the NJ AWB was being debated in the statehouse (1980's), and I VERY strongly suspect that the NJSP and AG wanted to "manufacture some statistics" to back up their arguments. Things might be different now... but color me burned.
In any event, I would be VERY circumspect about "manufacturing" a firearm in NJ. No way, no how for Willie. Ya'll go ahead and let me know how it works out for you. I'd require a letter stating that it was OK from the state Attorney General before I even thought about it.