The spheres might as well be thrown away, the chance that they will still have a nitrogen charge is almost zero. It would be foolish to just install a used valve without knowing the age or time since rebuild. Unless you want to rebuild two of these valves so they are ready to swap out with the ones on your car now they are not of much use as is, they are only good for use as a rebuildable core. You can remove the ones on your car now, rebuild them, and have them back on your car the same day anyway so they would not be much of a time saver. You would be further ahead spending the money on a new pair of spheres and a couple O rings to rebuild the valves on your car.