Yes you can but. Relocating spreaders requires some engineering. Some mast makers weld in compression
tubes so would require some professional help to move. In any case there has to be some way for the mast to take the compressive loads of the spreader. There are different mast sections both in dimension and wall thickness. Determining if a used stick will work for sure would need doing some calculating which is way above my engineering skills. If you are cutting a stick down, it's probably going to be strong enough but that will mean extra weight aloft that you don't need. Countering a pound at the most head
takes many more pounds in the keel
. There are a lot of boats out there sailing with masts from other boats. If you do go that route
better have a good idea or professional help on what you are doing. In the least, I'd get the advice of a experienced rigger and, to be absolutely safe, a few hours of a naval architects time.