Other Car Rental Programs/Partners (ie. Alamo, Enterprise, Sixt) - Renting a Dodge Challenger or Chrysler 300

Does anyone know how to get one of these in SFO if you make a reservation for a certain class of car? My friend is coming in and wants to test drive one
of these vehicles. He says it never seems to be available even though they advertise these vehicles types as available to rent. I know they are subject
to availability, but anyone have any tips for actually making it happen?

You didn't mention with whom your friend is renting.

A Chrysler 300 6cyl is normally a Premium with Alamo...and a Charger is normally a Full Size.

The Chrysler 300C is sometimes considered a Premium Specialty or Luxury as it has a lot more bells and whistles on it and costs more for the rental car company to purchase. The size of the car is not the only deciding factor in the class of the car. How it's equipped is also a factor.