Installing XR650L front forks on an NX650
If you want to do this fork conversion on your NX you'll need the forks, triple trees, axle, speedo drive, speedo cable, wheel spacer, bearings, and brake caliper from the XRL. You'll need to do a little grinding so the ignition switch won't rub, but otherwise it bolts right in. The steering lock will no longer line up, but that's not a big loss.
The biggest thing to consider is that these forks are 2" longer than the NX's. To fix the geometry issue you can shorten the XRL forks, do a supermoto conversion*, or put a taller shock in the back to jack it up to match. If you did nothing to correct the geometry, the longer front forks would give you more trail, and therefore more high-speed stability, but the bike would not corner as sharp at low speeds.
* The 17" front tire will drop the front end 2 inches.