This article goes into detail on how fonts work in mac os x:
http://www.macworld.com/2002/07/secr...tion/index.php
I don't think Classic fonts are directly usable by OS X because they must be stored in the Classic/system/fonts folder and are a different file format. They are usable by Classic and it's apps running in Classic Mode, however. But try copying them to the font folder you create (described below) and see if they load in OS X. If they do, you're in business unless you get a font error thrown at you upon RIPing a file for print.
Also, get rid of FontBook! There's a better option out there which will greatly improve your font experience, called Linotype Font Explorer (
http://www.linotype.com/fontexplorer). Install it and first run Tools/Clean System Fonts Folder. It will remove all but the necessary system fonts from OS X. (Speeds performance since you won't then load all your fonts at start up, for every app.)
Then create a new folder called MY FONTS, or something similar, and store all your fonts there. Then load them into FontExplorer. Your font performance and utilization will greatly improve. You can even scan your fonts for issues. I love this app and have used it for the past 3 years without issue. They update it regularly.