The full sized bodies can take a 22 fret conversion neck. The 7/8 neck uses a similar blank as a 22 fret 25.5" scale with a 24 fret 24.75" scale. The bodies for each don't intonate with each other.
One area of incompatibility for a 24 fret extension for a 24.75" as for the 25.5" scale 24 fret extension is the neck pickup position. In any event, it is not an offering from Warmoth.
Video on the 7/8