Hi @Anonymous,
Welcome to the Fusion 360 Community!
I have one idea here! Probably one of the more simple options for your already built loft, assuming that loft is the correct shape that you want (minus the part that went into the inside), would be to edit the loft feature from your timeline (right-click it in the timeline) and change the operation from Join to New Body (assuming that it is not already a separate body). Then, you are going to want to go to the Modify menu and select Split Body, choosing your Loft as the Target Body and the Horseshoe body as the Splitting Tool. This will then create a separate body for the piece inside the horseshoe shape, for which you can then Right-click that body from the browser tree and select Remove (hitting delete will make Fusion try to heal the model). Then, once the unwanted pieces are removed, you can do a combine from the Modify menu to join the loft and the other body together for a smooth intersection.
I'm sure there are other ways to do this, including using rails as well as moving the loft profile, but this is the first one that came to mind for me! Simple, although adds a few extra steps to the timeline. Check out this screencast below for more details!
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James Youmatz
General Adoption Manager | Informed Design