Apologies for not directly answering your question.
My advice would be not to bother renting a car or taking your own.
It's the same advice I was given by a friend living in Florence, before I visited.
In Florence AND Pisa as a visitor, you're almost guaranteed to get ticketed. ( months after the fact)
There's a system called ZTL in both cities, which dictates who can drive in what direction,
in what streets, during which hours. Even the locals aren't 100% sure how it
works, so not much point asking them.
There's a good express train service between the cities, that only takes an hour or so.
In either city, having a car is a liability more than a benefit. Public transport (buses) is
a much better bet, for getting around either city and the routes etc are easy to navigate.
My ten cents worth