I just sent out 3 uppers to have tac brakes installed on the barrels. Just so the armorer would'nt have to keep up with the bolt carrier assemblies, I bagged and tagged each one with the upper it came off of. Question, after they do the work and re-assemble the barrel without having the bolts that came with them, will the head spacing still be correct or should I ship the bolt carrier assemlies to them so they can double check.Hope this post makes sense, I don't really understand the head spacing thing. As always, thanks in advance for any help
BASE-RIGGER

With the way that the AR is designed simply removing the barrel from the upper will not change headspace. 99% of the time swappping different bolts between rifles doesn't create unsafe headspace if the parts are all manufactured correctly.  Many people post that they went their tours in the military with people showing no regard for swapping bolts between rifles after cleaning during qualification. (I made the personal decision to invest in some headspace guages so that I KNOW if my rifles are safe.)

So if I ever decide to change barrels on my AR, I don't necessarily need to have it headspaced?

You CAN NOT headspace an AR.  Its fixed.  Do whatever you like, change barrel nuts, uppers, float tubes etc your headspace can never change.