Hi Lstitt,
20x9" on -12 will definitely fit.
In fact I have a set of American Racing 20x9" -12 offset wheels all good and true, used, take off's from my truck - I used them for nearly 4 years with no issues, decided to go to more standard sized rubber.
Currently the wheels have Cooper 305-50 20's fitted. If you're interested drop me a PM. 2 tyres are worn, 2 have 20%, includes the full set of lug-nuts and 2 hex-keys.
Here's a pic of the 20x9" -12 offset wheels fitted:
https://plus.google.com/107764113830...362?banner=pwa