with Murat on the Throne Naples will be the best nation candidate to form Italy.
I dunno though. As even in otl Italy much like Greece needed an external sponsor/ally to help them get the ball rolling. Italy here is even more multipolar than in otl, and compared to the Savoyards the Cabonari would probably coalesce in Naples along with a bunch of other dissaffected Napoleonic veterans and Bonapartists finding themselves increasingly unwelcome in France.
Though after the Congress of Vienna, I doubt even the Murats could so openly act against the Papal States. And despite Carlo-Alberto's liberal leanings, he only really at first seemed to try to try and ride the revolution's coattails to attain Milan (lombardy) from the Habsburgs, a longstanding goal of the Savoyards since the days of the Sun King. Now that I think about it, this might actually divide the Revolutionaries between Turin and Naples similar to how Austria and Prussia divided Germany.
There's also Sicily right next door which probably would out of spite, start aggressively modernizing and building up its forces essentially sparking the War of Sicilian Vespers 2.0.
Napoleon III wasn't really trying to unify Italy as a unitary state capable of being a rival to France. What he wanted was more or less a confederation of states, keeping the pretenses of Italian unification, while being small enough for France to influence. Napoleon III actually could end up winning big here by playing all these factions against each other while also allowing for the Pope to survive as the sole "neutral party" within the peninsula. The Pope could end up the leader of the Confederation similar to how in the Confederation of the Rhine von Dalberg, the Prince of Regensberg served as the Prince-Primate, its nominal head as the successor of the Elector of Mainz, the Primus interpares of Germany.
The Greeks will refuse his candidates cause they want someone who is related to the Palaiologos, Komneni et cetera. maybe after the first abdication and the need of a new king they might accept his proposal as it would be a very liberal king.
There would probably still be the other Great Powers who'd want another candidate to be King, still being distrustful of the House of Murat. Though to seal the alliance, I could see the new King possibly marry into the Murat family to shore up a dynastic alliance.
As long as he stick with the french and Russian no one will say anything as he is simply helping the Greeks. the major difference is Greece becoming an ally and friend in the long term if the "magna Grecia" relation is exploited.
Ngl Greece and italy parallel each other with their irredentist dreams. The end of the Italo-Romance presence in the Balkans (istria and Dalmatia primarily) is quite similar to the aftermath of the Greco-Turkish War.