I seem to have found a fix:
Changed core-1.1.0.aar to core-1.1.0.zip, edited the manifest to remove the meta-data item, rezipped it, renamed it core-1.1.0.aar
In Google ARCore SDK Plugin: 181012000
In Wikitude plugin: 180226000
I assume the version ARCore plugin I'm using needed a newer minimum version so I opted to remove it from the Wikitude thing, assuming Wikitude will work fine with a newer version (and it seems to).
Seems to conflict with the ARCore unity SDK -- is there a place in Wikitude's unity plugin files I can remove this conflict?