Originally Posted by
m907
That's Avis (and National at some non-aisle locations). Hertz doesn't have that option.
Before UC, the carfirmation email included a link that let you select a different car from some available options. (It might still, I haven't been to a non-UC non-HLE in a while.) That said, it wasn't particularly useful and I don't think I ever changed my car this way.