Sorry it is a bit confusing, I still don’t understand what you want to do?
If you want the 60 recorded frames per second in a 24fps project then why conform before importing?
Now if you import the 60fps in a 24fps timeline and mark so it will playback all frames in your 60fps footage it will extend. This is normal no matter which Application.
If you don’t know which clips are in 60fps in your timeline or event manager… sound like you might want to look at your media management. FCPX is has great tools and is easy to use to find your media by it’s attributes and metadata.
Did you jump by fcp.co yet?