Well, I begin with the fact that I don't believe in those groupings. All those things about Ibero-Romance and Gallo-Romance have no real sense to me, because I believe in the continuum thing and trying to group the languages is, as we say in Spanish, putting doors in the countryside. So while I don't see Catalan as fully Iberian, it's not totally Gallic to me, more like a bridge, like a medium gray in a grayscale.
Jack, let me disagree with you in that thing about the Catalans coming from the Pyrenees in the 8th century. Which are the sources for that? It's not like they are a clear ethnicity like the peoples in Siberia; I'd consider equally Catalan the peoples who lived in current Catalonia in the 7th century; after all, they were all Hispano-Romans with no clear borders and their language wasn't formed as a clear separate entity yet. Sounds odd to speak in ethnic terms about the Iberian peoples after the Roman conquest, except for the Basques, who weren't assimilated.