Old shutters are well old. I wouldn't count them to be 100% perfect but then some people claim brand new shutters aren't 100% either. If you're able to test the thing out then that will give you an idea. Likely the speeds will be off but if they are constant then that's okay. How hard a new shutter will be depends on which shutter you need. Those real big ones aren't made anymore. Neither are the #2. Best person to ask about new shutters and old ones is somebody like Skgrimes.

www.skgrimes.com