The center of the reciever on my 06 with a Hidden Hitch is 16". You may need a long ball mount to clear the spare tire. I have a 12" one and it gets the ball right at the rear of the spare. They are measured from the center of the ball hole to the center of the pin hole. Normal is 8"
I believe it's Draw Tite that even makes a reciever that is 3" or so back farther for this reason. If you want, pmail me and I can send a picture to show how close it is.
EDIT. I just went here http://www.hensleymfg.com/whatisthearrow.html and saw what might be your setup. If the distance from the "hitch bar" to the front edge of the "hitch box" is 13" or more it will clear the spare. To put it another way, the distance between the spare tire and the ground is 22" and it extends 13" back from "hitch bar" (pin).