The 18" spare that was used with the Charger will fit all LX vehicles, except the SRT8's. The front brembo's wont allow it.
To save the 400+ most will charge to fix this... Just buy the 18" spare from ebay, a junk yard or anywhere, and use a 1.25" stand off adapter.
I would never run stand off's at speed, but I would not run the spare over 60-65 mph anyway.

SRT8 owners....when running a spare that is not the exact diameter of your other tires, you must disable esp to avoid damage.