There is a freeway around the SW side of the Florence metro area that connects A1 with SS75. To the best of my knowledge, the name of this highway is Via Marco Polo (although it might change names halfway through and the bridge part definitely has a different name... Italian signage is not very helpful), and it has the Italian kilometerposts (is that a word) that all government-maintained roads have. This is the primary way to get into the city center if you're coming from the south (like from Rome), so in my opinion, it would make sense to add it.