can i just buy stock sensor or will i have to go with aftermarket ones?

 

i bought some off ebay that where of a sedan that had aluminum wheels. they work fine in my 18 inch axis

 

Actually all you have to do is buy new valve stems from your gm dealer, then swap the sensors from your original wheels. They unbolt from the valve stems.
Or you could go to tirerack.com, they have aftermarket senors.

 

these would work right http://shop.advanceautoparts.com/Pro...e=2264&PTSet=A