want to finally get one for my second lower i have. nothing crazy just something simple.

You looking for someone local? I'd bet most if not all manufacturers have a Jersey compliant offering.

The only evil features on the upper are going to be bayonet lug or threaded barrel/flash hider and it's only evil when paired with a detachable mag and each other or a detachable mag and pistol grip if only has one.
Now I suppose the state if they kicked in your door and see a completed lower and your upper in a box could argue you have an assault rifle, but an upper by itself is not illegal and anyone  you wish could be made NJ compliant, by removing the lug or pinning some other muzzle device.

Again there is a risk the police decide to execute a warrant when all parts are delivered and make case.

Edit this is assuming you're not making an AR pistol or SBR, so I'm assuming you have a 16 inch barrel. You'll need a pistol permit for the AR pistol  config.

@ferrisx you sure about that whole pistol permit thing? i don't think you can put together a AR pistol that is Jersey compliant, with or without a permit. I might be wrong but weight and/or length requirements can't be met.

You're basically correct, there is one compliant pistol that had a polymer lower and no shroud. It was the busmaster carbon 15 97. Goofy looking as hell.
I also suppose you could make one based off the california fixed mag systems, but I'd run that by the NJSP first then again every opinion they give they claim is an opinion and not legal advice.

I should've better explain that above.

Here is the law btw
A semi-automatic pistol that has an ability to accept a detachable magazine and has at least two of the following:
(1) An ammunition magazine that attaches to the pistol outside of the pistol grip;
(2) A threaded barrel capable of accepting a barrel extender, flash suppressor, forward handgrip, or silencer;
(3) A shroud that is attached to, or partially or completely encircles the barrel and that permits the shooter to hold the firearm with the non-trigger hand without being burned;
(4) Manufactured weight of 50 ounces or more when the pistol is unloaded; and/or
(5) A semi-automatic version of an automatic firearm; and

In a practical sense, you're absolutely correct - but I'm going to take this opportunity to yell at the rain, just because it's one of the (MANY) things about NJ Firearms Law that irks me.

The ACTUAL statute (i.e. "The Law") merely says, "Any firearm manufactured under any designation which is substantially identical to any of the firearms listed above." (that's 2C:39-1w(2), FWIW).  The whole "mag. outside the grip, 50oz. weight, barrel shroud, flash suppressor" bullshit is an OPINION of the 1996 Attorney General, in a directive to all state and county prosecutors, instructing them what HE thought "substantially identical" meant.  To my knowledge, that part of the was challenged exactly ONCE in Monmouth County, and the judge found the law to be unconstitutional due to its vagueness.  Of course, that was not a precedent-setting ruling (was only a superior court ruling).  That was in 1993 - prior to the 1996 directive (the 96 directive attempted to "clarify" what was meant by substantially identical).  The problem is, an opinion of an executive branch officer doesn't mean jack squat - it would be up to the legislature to "clarify" a piece of legislation that a judicial branch says "no go, too vague".

But, since none of us (me included) cares to be the test case here, we all operate under the assumption that one guy's opinion is the law.  So be it...  no one NEEDS a (insert any desired feature or attribute you'd like) to exercise their 2A rights.  After all, the 2A was written when all we had were muskets, and it was only meant for the militia, which means the army.  So there...

No you don't.

we all do, and so should you

I've seen those skeletonized upper/lowers and often wondered if it can work out to a legal pistol with the right combination.

Alas, I'm not a rich man and it never made it part thoughts.

It would be a smidge easier if those manufacturers put the weights on these things.