Hmmm.... Have the radicals in Milan and Venice win in '48? That would be tough, though.
Or Charles Albert moves earlier and more decisively, kicking the Austrians out before Radetzky could get them settled into the Quadrilateral, then gets Lombardy and Venetia to join 'Piedmont'. Then, in about 1850, renegs on his constitution, and tries to rule autocratically. Republican revolts break out in Milan and Venice and Genoa, followed by Turin, and Charles Albert is kicked out completely. The new nation relabels itself as the Italian Social Republic.
Yes, I know you meant Mussolini's. But this would work, no?