Can you switch a shaft from one golf driver to another golf driver?

Yes, in principle you can take a shaft out of one club and put it in another. If it's a steel shaft, it's almost certainly cheaper to just replace it with a new one. For graphite it's not beyond the capabilities of a well-equipped shop, but it would still probably be cheaper when it was all over to put a new one in the other clubhead. Unless it was a really special shaft. And I can't define "really special".